Resolution help

So, the res upon going fullscreen is kind of broken, upon going into fullscreen (alt+enter) at the max res, it doesn't go into my desired res. In fact, it's way smaller, as if I pressed F5, and now it's stuck at that small screen, even in windowed and fullscreen forever.

This affected all of my other games, some going at way smaller resolutions then what I put them to. I have been stuck with this bug since 4.0 and I really want to know how to fix it.

(Also, this is my first post , so sorry if I posted on the wrong tab.)