What is your PSU? It can be failing and causing the reboots.
It's a Corsair TX750M. How can I tell if that's what is causing the crashes?
Here's some more info regarding the crashes:
I can tell it's about to crash when the computer semi-freezes. I can't really click anything other than some random things. I can't ctrl+alt+del to pull up Task Manager, but sometimes a dialogue box pops up asking to "end task," which I obviously can't click.
When it finally crashes, the whole screen goes black except for an inch strip at the top full of artifacted random colored pixels.