After a particularly bizarre incident where my MBR became permanently damaged, I found myself reinstalling Windows on my computer that has been otherwise very good since I built it in September. No issues... until now.

I installed Windows 7 the way I did the first time, and right before I went to bed, I had it check for updates. This takes a long time the first time you do it on Windows 7, but I figured it be done in the morning. When I woke up, I shook the mouse, pressed some keys, but I couldn't wake it up. The power indicator was still on, the fans were spinning, but that's all I could really tell (my monitors were blank).
I forced it to shut down and I haven't been able to power it back on since. I've tried the button on the motherboard and my case, nothing (as in it's actually like I didn't press the button at all. Nothing.). When I looked up this issue, most people tried dropping in another PSU and it worked. I don't have any lying around and I don't think it'd be fair to ask someone I know to pull theirs out of their computer to try it on mine. I did, however, try my power supply on a friend's computer. Powered up just fine, in fact.

If anyone has any ideas how to get my computer up and running again or at least knows what the problem might be, I would greatly appreciate it. Thank you.