I've had my computer for a while now and recently I've started having a problem. When I'm doing something that requires a lot of processing like playing a game on high settings or just running a lot of heavy applications my computer will just shut off. And in order for me turn it back on I have to toggle the power supply switch off and on to get it to power back up. I built new system for my friend about a year ago and it does the exact same thing??? I've recently formated my hard drive and installed a newer version of XP on my system and it's gotten better but still does it occasionally. I thought this was just a power supply thing until my friends computer started doing the same thing. Any ideas?