Having resolution issues with Five Nights at Freddy's 4? This quick and easy guide should help you solve the problem of having the game run in a tiny screen or a bordered window and allow you to play in full screen mode.
To fixed the bordered windowed issue, do the following steps:
1) start the game up
2) press ALT and ENTER keys on your keyboard
3) click on the Fullscreen icon at the top fo the window
That's all you need to do.
Many players on the Steam forums have reported this as a bug, so expect it to get an official fix once the developer comes around to it.