Games with low resolutions not working

[NerfedFalcon]

I know how annoying it is when you play a game with a low resolution and it throws all your windows around, but my computer started doing something even worse: it just doesn't run games at all unless they're either windowed (which is hard to force) or in 1920x1080 right out of the box. And the weird part is, it didn't have any trouble before. I can't remember when this problem started, but it's definitely a recent development.

Google only gives me results on the current console war and 720p vs 1080p on a HDTV for PS4 and XB1, so I decided to ask some of you guys: how do I fix this problem?

Edit: It's not a perfect solution, but I have figured out a workaround involving the task manager and Alt-Enter that works sometimes. If anyone has an actual solution, let me know.

 

[NerfedFalcon]

So basically I have to change my resolution to every possible option with brute-force trial and error until I figure out what the default is of the game, and change it to 1080p from there? Well, I guess it's better than nothing.