Full disclosure - I am not super technical. BUT - this was happening to me, and we found the solution. I have a Windows 8.1 Lenovo X1 Carbon for work - and it works really well in the office (and at Google powered Starbucks), but will not work at all at home. At home, I have at least 10 APPLE devices that all stay connected to my Apple time capsule without issue. Windows 8.1 - not at all. Well, it works for 20 minutes and drops. And when on VPN, forget it. I heard from a networking person who spoke to my husband that the problem is: Apple routers are programmed to change channel automatically when they see a lot of traffic on the system - and Apple devices know this - and know to follow the protocol. Windows devices do not do this and use a different protocol. Solution - change the channel to a consistent channel - and don't let it automatically change. Tah-dah! Works like a charm. Here's how. http://www.imore.com/getting-slow-speeds-or-dropped-connections-your-airport-extreme-or-airport-express-heres-how-fix-it
Hope this helps!