Okay my EMachine has a nasty habit of turning itself off during running high performance applications. Playing games is when I mainly notice it happening, it'll be running fine for awhile, then I just get a black monitor and the computer essentially turns off. (the blue power light remains lit for a little time, but I'm disconnected from my applications.) So I'm wondering if it would most likely be the PSU or if there is another explanation for this. For the record the computer has never to my knowledge turned off during any light usage periods, it runs fine browsing the web and playing the pre-installed Windows games. And it's running XP in case that matters.