Please quote 40'x20' clear bifold door with manual side latches, internal truss, strap lift, weather-seal kit with labor. Please also quote as an option free standing header with labor. Please send design information so we can send to Metal Building supplier in case we don't do the free standing header option We will provide and install external panel and trims
Have an existing wood frame hangar with homemade bifold door on endwall. Getting anxious about operation and soundness of this door. Looking at your website, it appears your bifold door with liftstraps and a freestanding header would be a replacement option for my situation as current posts, truss,and chord don't really lend themselves to attaching door directly to hangar. Would "build your own door" be an option on this? Would appreciate prices and availability info. Thanks, Jack
I have a customer in need of a 40'x16' bi-fold hangar door. I'd like to know if your system is self-supporting or if it will require a freestanding header depending on the structure. Thanks, Cody
Looking to replace an aged wood garage door 8' x 18' with an outward bifold door. Could you help with some pricing on the liftstrap door and options for your freestanding bifold door header for my client.
A customer of mine would like a ballpark estimate on installing a bifold door on an existing wood frame building. I'm sure it would need much reinforcement starting with a free standing header. Thanks
My beams in the front where the door will go are 6x6. I have been told by some friends to reinforce it with I-beam, so that is a possibility if I need to go that route or could I just get by with a Schweiss freestanding header. Thank you very much
40'x18' clear, prepped for interior liner panel. Price as bifold strap door. with option of free standing header installed. Please send design information for Butler for building design. Thank you
2x6 wood structure need to make door oping taller. inside roof 113'8'' Need bifold freestanding door header to match inside height. Door on building is white panel now. like to match that look. like to know more about what options you offer
I recently purchased a home which has a Quonset hut style garage. One end is open and I'd like to see about having a bi fold liftstrap door installed on that end. Wondering if I'll need a freestanding header. I can send photos.
Hi, We have an existing detached garage. Used to have a garage door. We would like to put a bifold liftstrap garage door back in. The framing of the old garage door is still there. I think I will need a freestanding header for it. Thanks, Scott
We are checking our options for a new door on an old wooden structure that likely needs a freestanding header. The door opening is 18w x 14.6h We would like to know about your bi-fold door. Is it electric open only or manual latching door optional? We want it to be insolated. We don't want to lose head room if possible. are there window options ? Thanks
I need a free standing header for this door manual latches 2 inch cross tubing flashing for liner top and bottom seals no tin. Motor 220 or 110 volt ? THANK YOU, Rick
My hangar is a wooden frame structure. I am sure it will not support the weight of a bi-fold door without the incorporation of a freee standing header. I imagine it will need a steel frame to support the weight. Would someone be dispatched to review the potential install? Door opening is 44 feet ground to base of trusses is 12 feet
Please price a 50'x18' clear Schweiss bifold door, strap lift, internal truss design, bottom drive,auto cable latches installed labor and material. also need price for your Schweiss free standing header design and its installation. Please also include design specifications and estimated bifold door delivery dates. Thanks
I am in West Nebraska need one possibly two agricultural doors on a Chief building built around 1975. One is 16 ft and one is 24 ft wide around 14 ft tall. Wondering if I will need a freestanding header for this bifold door?
I'm building a wooden hangar 48' wide and plan to put your 46 x 16 bifold door (hinged at the bottom chord of the double truss) on it after it is finished. I see from your diagrams that I need to install triple hinge supports that are tied back one truss. My question is what is the spacing for a 46' door hinges so that I can install the triple backing supports before the side is installed above the door opening? Can you also price me a freestanding bifold header? Thank You Timothy Downing
I have a Mueller metal building with a 30' wide by 10' high opening. The header in the opening was not designed to carry load. Although the columns at both ends of the opening are very robust I still believe I will be needing a Schweiss freestanding header. I am interested in any design, single panel hydraulic, or bifold, whatever works that is affordable. My goal is to preserve the full width, and as much of the height as possible.
I need a hangar door that is functionally self-supporting. I have a wood frame hangar, 39'x10' opening with no current door. I can not give up any vertical space, and I am concerned about depending upon the structure of the building at the top connection points. I envision a free standing header. door, likely bifold, that would be set on concrete about 12 inches in front of the hangar and fully operational. I would dry in the gap to the hangar, but there would be little strain on the hangar structure at the top. Have you done something like that before? I would like Schweiss to construct the bifold door frame and free standing header from box steel to your engineering specifications.
I have a Behlin Quonset I'm looking for a bifold door with a freestanding header to be mounted on the side of the quonset. The hole size is 23'9" x 14'6". I like the strap style and I need a man door. Interested in pricing.
wood hanger at Newport OR airport with old wood bifold door. need to replace approx. 40'. I'll send photos. I'm afraid I will need a Schweiss freestanding header for added support.
We are looking to retro-fit a bi-folding door onto an existing airplane hanger that currently has sliding doors on it. You have a very nice website with lots of good information it but I wanted to talk to a person just to make sure I am interpreting everything correctly. From what I am seeing I will need a new heavier duty freestanding header going across at the correct height and some additional bracing to tie that new header back to the adjacent bar joists. If someone would please contact me we can work out what I actually need and then get a quote put together so i can start moving forward with my customer. Thank you and have a great afternoon.
We would like a bi-fold strap door that is flush to the exterior facade. It's a steel frame building, but the garage opening doesn't have side columns directly adjacent to it, as the garage is held in from the building perimeter, so it might need to be wood-framed at the side. However, we do have a steel beam above the garage door, 7-7 11/16" above top of garage ramp. Depending on how the wood side columns are detailed, we would be open to adding secondary tube steel or freestanding header for garage support.
Looking for 2 Bi-fold doors on a wood frame building RO sizes are H 13' 11 5/8" x W 18' 3" H 13' 11" x W 18' 4 1/4" Will probably need a free standing header. Hoping for pricing asap. Thanks,
Price of a single 34" X 16 " bifold liftstrap door. Does door support itself as other do having a post of 12 x 12 1/4 inch steel beam 10 in ground or should we be looking at a freestanding header. Someone told me we can put door in wide open area and it will self support itself.
Trying to budget a redevelopment of an old aircraft hangar. Looking for a general quote on 59ft x 18ft bifold with liftstraps. I may need a freestanding header for this old wood building, price that as well.
Please provide any autocad or revit door details for your folding liftstrap doors as well as any relevant price information on adding freestanding header doors.
I have about 60" of gable height at corner of door opening. Am open to either side column bifold door type and would prefer for the door to have Schweiss freestanding door frame. Would also like to have 2 window opgs framed into the bifold liftstrap style door frame (24x32).
I am looking for a door for an machine shed. The opening is 14' high and 46' wide. It has a glulam header that is 5 1/8" by 30". The shed roof trusses run perpendicular to the header and tie into the larger shed. Should I need to beef up the header more or get a free standing door header to accept my machine shed door?
Would like to keep head room but do not know if there is enough room above door header at the eave to have a bifold strap door. The barn is about 25 years old 6x6 wood poles. Should I consider a Schweiss door with a free standing header?
On 50x18 Bifold door I just called about, I forgot to mention: 1. Please option free standing door headers and labor to install the free standing headers. List the headers and labor to install separately. 2. Provide steel door design information so we can send in. 3. Need 18' clear on bifold doors Please return revised quote today.
We need information regarding clearances for your Schweiss bifold strap door systems. How much head room is required etc. if we use a freestanding door header on an old wood building.
Looking to price 25x18 hoop building door. A Schweiss steel bifold strap hoop door with a free standing door header is required.
I am looking to replace a standard sliding double door entrance ( 46 ft wide ) on a wood building with a larger Schweiss bifold strap door with additional height from 18 ft. to 20 ft. May need free standing door header for this.
Need a 38x18' bifold strap door to be added to the side of an existing building. I want an independent freestanding door structure to support the new door.
Please quote a 50x18 Clear Schweiss Hydraulic one-piece Door. Please quote labor to install. Please also quote a free standing header and the labor to install it. The door will have interior liner panel. Please price accordingly. Please FAX design specifications so I can send to Butler for building quote. I saw the feedlot doors you did for Revier, they sold me on your product, that and the fact that you are an established business with a great reputation.
Looking for a price on either Bi-fold (Liftstrap) or Hydraulic door, the opening will be 18'x13'6", and they need full opening height so the door would have to be mounted on the exterior of the building. I just need the pricing of the doors for now, we know that the building would need a great deal of reinforcing, and just want to know if cost-wise if this or a freestanding header is a feasible option. Thank you
Looking for a price on a 50' x 18' Schweiss liftstrap bifold hangar door. Need structural steel header system to retrofit into a steel building. No insulation needed. Cost of door shipment to southern Calif.
On a 14 ft. tall opening, how much room above the opening is needed to have the full 14 ft. of clearance when using a Schweiss liftstap bifold door? What if I need a freestanding header?
I want to convert a 40'x70' pole barn to a aircraft hanger. Intend to put a 40' Schweiss liftstrap bifold door on one end, high enough to also beable to fit a motorhome through it. Guessing at least 14' high. Probably would want to incorporate your freestanding door truss. Open to any ideas, looking for a good but inexpensive solution. Thank you,
Need to close a 12ft wide by 9ft tall opening in a metal storage shed. Can't simply hang a garage door because there is nothing to support it. So, I was thinking of using your bifold door and free-standing headers. Also, the shed is located at least 50 miles from the nearest city. It is totally off-grid. How can you help?
Hello, We're looking for a quote on One- 18'Wx13'T and one 12'4"Wx13'T insulated Schweiss bifold door for our paint building. There will have to be some modifications to our building as far as the mounting a header for the hinge system, because of the locations of the doors, they're both all the way to the one side of the building that has the pitch of the roof contour. The door opening goes almost all the way to the lower roof line, then there's approx 4' above the door on the other side of it. Both doors openings are setup right up to the side wall of the building. So I'm thinking we'll have to build some kind of free standing steel header frame around the door opening for mounting these doors to. Feel free to give me a call to discuss the specifics if you'd like. If I'm not available you can also ask for our general manager. Thanks!
I have an American Steel arched building. I do not have the end finished. I think I would need a free standing header for my door 16 X 16.
Hello, Im interested in a Schweiss Bi- fold doors and am thinking about installing some on a barn we have out in the country. My question is what size header do I need to operate the Bi- fold system normally? what is the thinnest support system one can essentially use? can you please tell me the price of a free standing header.
A client is looking at using one of your Schweiss straplift bi-fold doors in the interior of a building - We would need to install a support frame as well as the bi-fold door. The door size is roughly 24 wide by 12 feet tall
We have a local customer that would like us to furnish and install a Schweiss straplift bifold hanger door on a small hanger that is constructed of siding and wood posts. The Hanger is not insulated or heated. The opening size is 42'0"w x11'5"h and is framed with 6"x 6" posts. We have approximately 24" of headroom to install the free standing header for your door. Please quote furnish only 1 Bi Fold door to fit this opening. Please including freight to: Michigan
My hanger has old heavy doors that need to be replaced with a quality Schweiss door. The slides are warped and we have to open the doors using a fork lift. The clearance is about 13 feet x 60 feet wide. hydraulic doors might give us our best clearance. Can I use a free standing header or will what I have work Could you give me a rough estimate what these doors might cost. I have 3 bays.
Don't know what "end wall" or "side wall" means. Guessed at "end wall". Bi-Fold Door will need to have a free-standing header as the hangar door is very old and not structurally capable of supporting a new schweiss door.
I'm in the design phase of a new project and I'd like to use a schweiss bi-fold doors but need to know all the structural/framing requirements so I can be sure everything is an exact fit or if I need a free standing header. I'm most interested in how weatherproofing happens around the edges. Thanks.
We have a customer that wants a bifold door in the end wall of a 50'X 100' X 26" Building. Do we need a free standing header or to get special framing quoted on the metal building. Also we want the door 40' wide and how tall can we put in a 26' high Metal Building.
This is a remodel of an older hanger home which had commercial roll up doors, now removed. The house is a day-light basement configuration. Attach points will be concrete walls, one paraell with the door and the other perpendicular. Perhaps a "free standing header" would be of interest. Am interested in a Schweiss liftstrap bi-fold door with man door, windows, auto-lock and perhaps remote. The best deminsions I have now is 40'0" x 9'10". Of particular interest is salvaging as much vertical clearance as possible. Intial contact is best with e-mail since I spend most my life in the air as an airline pilot. thanks, Doug
Guest house turned into expensive toy (motorcycles, bmw, boat) storage. 8ft eve low slope to back, standard overhead won't work. 10-12ft wide bifold strap door would be nice. If free standing header is installed in opening only room for 7ft tall opening. Exterior would be finished in vertical siding.
This building has a bi-fold door on it now that was damaged by wind (not a Schweiss door). We feel it's best to replace the existing frame and all including a new Schweiss bifold strap door. Is this something that can be provided by Schweiss? Center-to-center of side columns is 41'. Please call with questions.
My building is 60' wide with 16' walls and a 2-12 roof pitch. I need at least a 14' clear opening from the floor. The clear opening width must be at least 50'. I would prefer to get more width and height if possible, will your Schweiss bifold door do this. I would also consider the option of a free standing header above the roofline to get more height and width.
The size below may change /- 1-2 inches once I pull some exact measurements. I would just like to get an estimate on costs. The Schweiss liftstrap bifold door will need a built-in framework and I would like to have that framework inside (I know I will lose some entry height). I read on the web site is this what the free standing header is for. Do you offer them pre-skinned? If so, what is the additional cost? Thanks.
You have supplied a price for a door to one of my distributors and I would like to know if you could requote this bifold door but we need it to be a free standing type. On the wall of our building where the door will be install the roof truss will have too much deflection to fix the door on it. Also, could you recheck the bid, was I quoted with liftstraps? I don't want any of those darn cables to wrestle with.
Dear Sirs I recently purchased one of your doors "USED" 56'x16' Bi-Fold and would like to get the mechanical - enginering drawings for a steel header to support the door it will be matted to a pole barn type wooden buiding with 1'-12' pitch wood trusses. I looked on yor website and I think you called it a "Free-Standing Header".
I am planning on erecting a new building this during summer. I will use very heavy built used rafters 40x96x16. I would prefer to use a free standing metal frame header for the Schweiss bifold crane door. I would like the door 28 feet wide 16 feet tall. I just want the frame I will finish the rest myself. Could you just give me a ballpark estimate on this. Thank you for your time.
Looking what it cost to replace sliding doors on a 30 yr old machine shed with some type of Schweiss bifold doors. I believe the door size is 27x 14. Is it possible to be put on a older building like this or do you think I need a free standing header.
Need full support frame to fasten and support door. I think you called it a free standing header. Need quote on delivery and installation by your qualified Schweiss bifold door installers.
Building is an older with what looks like to be home made rafters. The poles appear to be sound but i have not dug around them to fully check them out. I would like more information on the schweiss free standing header design also.
Building is addition to existing hangar. Existing building is 45 feet wide. Roof on existing hangar will be extended at same slope over addition. Height will be critical as eaves are 20 feet high. Estimate roof being 16 feet high on lower side of building where the Schweiss liftstrap bifold door attaches. May require free standing door with one end above roof line. Minimum open height is 14'6"(prefer 15') Also include cost of remote controls. Call if you need me to explain this further. Cell phone is best.
I have a customer that has an older building (post Frame) and has an endwall slider 15'6" x 14' and want to install a Schweiss liftstrap bi-fold door but cannot lose any headroom. 14' is a must. I seen the free standing header that I think would work in this situation. I have someone to install it so I just need a price for the customer.
We've been looking at standard horizontal double glazed, low-e, Schweiss glass bi-fold strap doors to close in our back patio opening (x2) (part of building, so structural openings) the openings are 8'H x 15W and 8'H x 10'W. I like the uniqueness on your product it offers a great solution to our project. I am definitely interested in looking at a free-standing header possibility, as well.
Need 40x17 Clear. Please price each Schweiss bifold door with a free standing header separately. List labor to install door and free standing header separately as well. Please send design spec's. Thank you
We have an existing wood frame pole barn that we are needing to add a Schweiss bifold door on. We need 14' of clearance and the door needs to be 18-20' wide. Looking for an isulated door as well. It will also have to have its own free-standing support frame built similar to what you show on the round roof buildings if that is possible. Let me know what cost I would be looking at. Call or email me with questions. Thanks, Jess
Need 18' Clear on Door. Please send design information for the door. Need price for a strap lifting bifold door and installation separately. Also need free standing header and labor to install priced separately as well.
This is going on an old farm machine shed. It is wood studs with metal siding. We have to open the existing opening to the full width of the building so it can now accomodate a small airplane. I think a free standing bifold Schweiss door might work the best. I would appreciate your opinion. The measurements I'm submitting are approximate but should be close. Thank you, Jill P.
Door would be installed for use on a heated shop area we need the head room we can gain by replacing an overhead door with either a Schweiss bifold or hydraulic door. We would need an exterior free standing header for either door. I assume a hydraulic door would be simpler and faster to put up?
I need to talk to someone at Schweiss Doors about hydraulic Red Power door and options. Also need a price on free standing headers for this door.
We sell and install metal buildings and we are expanding our metal building line to include hangers and we are looking for a good free standing bifold or hydraulic door to go with our buildings. The selection will depend on the method of attachment and the maketing commission.
In Spring/Summer I plan on installing a Schweiss liftstrap/autolatch bifold door on the end of my 40'x50' pole building for my airplane. Would like a ballpark quote for a one-piece door system for a 40'x 11' opening. Could you also quote me for a free standing header if needed. I plan on installing the door myself. I'm currently working 7-days a week and odd hours so emailing is the best way for contact. Any info needed let me know. Thanks, Brad
10X 40 DOOR OPENING. SCHWEISS BIFOLD DOOR WOULD BE IDEAL AND WOULD REQUIRE A FREE-STANDING STEEL FRAME TO BE MOUNTED OUTSIDE TO MAINTAIN THE 10 FEET HEIGHT OF THE DOOR
A Schweiss Bifold door will have to be mounted on a external free standing header. Would you give me a bid on the header also? Lift straps. Switch location left side. bottom drive. Blanket insulation. manual latch. weather seal.
Hello, I emailed you last Friday in reference to the cost of a free standing header for a 49'4" X 12'0" one piece Schweiss hydraulic door. If you could please get back to me on this issue I would appreciate it. Thank you. Have a GREAT day. Bob
What information do you need to provide a quote for one of your Schweiss free standing headers & a bifold strap door which will be attached to a round building like the diagram you have shown in the "Free Standing Headers" link? Also, can you ship to Qatar?
Please price door & labor to install Please price separately free standing header & labor to install Strap Lift Need 17' Clear
Need 18' Clear Strap Lift Please price free standing header Please list the free standing header and labor to install separately
we would like a bid on a by-fold door to fit a door opening of 10'X 40' on a wood hangar that will need a free standing door with its own header
I am looking at adding a hydraulic door to an existing building. I would like a 100' x 26' door. Please send prices on adding to the steel framed building as well as with the free standing header. I would also require the deadman controls and the back-up hydraulic hook-up for a tractor. The cold weather kit with seal kit is necessary as we see extreme cold temperatures and it would face the north where we get rain and snow with strong north winds regularly. Thanks
Just starting to look.Basic costs for 12x40 foot bifold door and free standing header? Costs difference between straps versus cable. May have an open hanger, but thought I would at least price a door. Not looking for "bells and whistles" just a basic door. Thanks. Ricky K.
Masonary block building end application. 38ft 4in wide and 11ft high. Would like a Schweiss free standing header, header would extend above roof line, approx 2ft high on ends. Would like a single beam header
Hello, I would like an estimate for a lift strap bi-fold door, 12' x 40' open space. Including: automatic latch remote free standing header insulated installation not required. Ship to Rochester, NY area no special exterior finish. Thank you, Paul G.
I have a client that wants a door that is approx. 72" in length and 16/ /- in height. It is at a exit that is divided by a grass area and standard height curbing. 2 lane traffic in and 2 lane traffic out. I imagine that we will have to have this out in front of the building as a free standing door system. This probably means constructing a header system that ties into the building and sits upon some steel post. Thanks for your help and attention in this matter. Mark
I am interested in your Hydralic one piece door with its own header I need a forty (40) wide and ten (10) foot tall door I need it to swing out. Blessings and Tailwinds Jack R.
WOULD THERE BE A ADVANTAGE TO USING YOUR FREE STANDING HEADER DURING THE DESIGN OF THE BUILDING? WE USE MBS SOFTWARE
I recived your info catalogue by mail..Could quote a price on the free standing header for door opening 38'wide 12'height.I am in the process of obtaining a permit for this new structure with the anne arundel county..
I would like a quote for both hydraulic and bi-fold doors. Please include cost of options available, including free standing header, uato latch, remote control, 4030 windows or preframed openings, inside truss, and top & bottom rubber seals. What is the minimum headroom consumed by the bi-fold? I would like the engineering requirements to provide to the building engineer. I have not decided on building construcion type, but I am leaning heavily toward wood. Thanks, Dan
Looking for a Quote on a BiFold Door finished opening is fifty feet by fourteen feet High. Need full clearance. Want the free standing Header,Have 30 inches clearance above header. Want the strap lifting System. (Note)12" Cement Block Walls 28" steel Carrier Beam Need Price Delivered
I have a customer wanting a quote on a hanger, and was looking in my AOPA magizine and found your ad. I am meeting with the customer in a couple of weeks to discuss his options on doors, and would need an idea on price for bi-fold and hydraulic type doors. I also would like a price on a free standing header as an option. The doors would be sheeted with 26ga. metal and can be installed by me. Thanks.
Dave, On the door closure mechanism: where is the exact placement of this mechanism on your free standing header? I know you told me I would have to place a steel gussett on the back to support the part of the brackett that sticks out beyond the header. My questiuon is where, from top to bottom should the bracket be placed to get the maximum length of pull to shut the door the last couple of inches? Thanks for all of your very patient help...I am almost done! Tim
FLUSH STYLE MOUNT DO I NEED TO FIGURE STRUCTURAL COLUMNS AND HEADER OR DO YOU INCLUDE WE SUPPLY SHEETING? RIGHT. CAN WE PUT LINER ON AS WELL? I AM FIGURING A FULL LOAD RIGID FRAME AT ENDWALL. NEED PRICE BY 5:00PM 10/13/08
Have a dome shape building with 10 -20ft. wide by aprox. 11.5' center hight curved openings. This 'Portamod" Steel truss (on 20' centers) is frabric covered and high density urathane coated reinforced. One of the problems is a small concave between the 20' trusses in the covering that complicates the water runoff or how to construct a retrofit that controls that run off with out leaks on this curved/concave using your canopy roof design and free standing header, door header channel and not create a water/leak problem. Unless it is possible to custom design a curved header/single door with hydrolic rames. with a under cross header to support this curved door and curved water gutter to control the runoff? Call Chris for this different challenge
I have 2 Tee hangars at Sky Manor Airport in Pittstown NJ and need two 40 foot bi-fold doors. Doors must be free-standing and self supporting.
I have a 12X40 hangar door that I am considering replacing with one of your doors. The existing truss is not up to holding the weight of a door so for either the bi-fold or a one piece hydraulic I will need a truss sytem with it. Please send pricing and specs when able. Thanks, Mark
Please provide quote and product information for both "M" style and Free-standing Style.
Please quote doors with the following: free standing headers weather seal kit top & bottom rubber 3'x6'10 Walk doors each (Bifold door size may be adjusted) optional price for automatic latches in lieu of manual
Please contact by e-mail only, thank you FREE STANDING HEADER, do you supply complete so that I would bolt to my wood frame and header .....
I am intrested in a free standing bifold door. net opening is 40'2.25' by 10'11'.WE have 2'3" of vertical wall surface above door opening.Hanger is on front line and we are not allowed to increase structure heigth as in an above roof header.PLease quote free standing header sepratly as we have capability to fabricate. ---------Thank You Bill W.
I spoke with someone on 2/11/08 about a door quote and they were going to E-Mail it to me. I may have given them the wrong E-Mail address. I am looking for a 30'wide x 12'high door. I also need a qoute on a free standing header. I would like lift straps and auto latch. My brother-in-law Justin S. just put up his new door last week and is very happy with it. Thanks Rob
Would you please give me a quote on a 44'x13'bifold hanger door with straps and include a free standing header. Thank you, Dale C.
I just received a quote for a door, would you quote a free standing header system to me ? If you were to deliver the door to my Wyoming job site instead of my to Montana headquarters would you have to charge me WY sales tax? Thanks Larry
I would like an approximate quote and how long until delivery would be at this time. Would probably be looking at using a free-standing header. On bi-fold it would be bottom drive with straps and external truss. Not sure of the wedge measurement yet.
Julie S., Hey girl long time. finally I am working on a couple of hangar projects. I need a price on a 60 wide x 18 clear when open bi-fold with lifting straps, and an alternate for a hydraulic Both with an optional free standing header. Thanks Keith Call me to discuss
Out side mount free standing header looks like the easy's to install. Also include 2 windows