This is a problem I sort of caused myself. Before when I opened something like Alone in the Dark, Windows 7 would warn me that it is switching to classic setting or something so I could actually play my game. It got kind of annoying for it to come up every time, so like an idiot I deactivated it so it wouldn't show up, but now I can't play. How can I make it show up again?

There are actually two instances of this warning. One when your GPU is running out of memory (gpu.png) and another when you launch something that's incompatible with Aero (bubble.png, warning.png).

If it's the former you are talking about, that one should be governed by a setting in the Action Center - hit start, type "action center" and enter, on the left, click "Change Action Center settings" and under Maintenance messages, make sure "Windows troubleshooting" is checked (and if it is, you may want to try to disable it, click OK, return back and enable it again).

If it is the latter, I don't think you can actually turn that off. You can turn off the notification, but not the switch itself.