Undead Computer

Hello,

I am experiencing a strange problem and was wondering if anyone has any insight into what may be causing it.

The problem is that while in windows the screen will inexplicably go black, but wont actually turn off (the power light remains on). The PSU will continue running, but in all other respects it is as though the computer were off. If I am playing music when this happens the sound will skip very fast.

This only happens when I run 3 instances of a certain game (Eve online), but not always. If I keep one instance minimized it doesn't happen. Also, it is a lot more likely to happen when there is a lot going on, which is pretty much exactly when I'm need this not to happen. :\

This is a new system that I built myself. My previous system was old and terrible, but never had this problem running 3 instances of the game. My current system does much better overall running 3 instances, but the whole computer-abandoning-me-thing is not a cool new feature I am enjoying much.

I'm suspicious of my PSU. It is obviously not coping well in its new home (moved it in from my prior system). It is extremely loud, always. The fan controller doesn't seem to work/make any difference.

I'm not very tech savvy, but I did build this system. Here are the specs I recall:
PSU - Antec TruePower 500something
CPU - Athlon II (AM 3)
Motherboard - new, but cheap, Gigabyte board.
GPU - GeForce 9500
OS - Windows 7

So those are the suspects. Any ideas would be greatly appreciated.

Jesse