Computer Shutting Down

I\'ve had a problem that has just started happening over the past few days.  Anytime I play a game, after about 3-5 minutes into the game my computer shuts off.  When not playing a game it will stay on and run solid for days even weeks on end.

I\'m thinking it\'s the PSU that might be on it\'s last legs.  I have a 7900gt that i\'ve had in this machine for over a year, so nothing has changed on the hardware end for quite a while.  This PSU has seen about 3 major hardware upgrades and is only a 420W Thermaltake.  

Is PSU most likely the culprit?  Or is there something else I should look into?

I had the same problem awhile back.

Turns out one of my fans went out and I didn\'t notice.

T\'was overheating.

[§ôµÏG®ïñD]

If it idles fine but under load conditions its resetting, its most likely the cpu.

make sure the heatsink is clean of dust, and that the cpu isn\'t overheating.

[Viper_Fujax]

my computer wouldnt start up a while ago...thought it was the psu, tried the cpu, messed with the ram, messed with the video card...ended up being the motherboard

Don\'t really know enough about computers to help you out, but i just wanted to throw that at you to see if u can run a diagnostic to narrow it down.

Well, I set my videocard back to stock settings and my computer has been gaming solidly, and just ran through the Crysis demo and COD4 demo with no problems.  I did a stress test on my CPU and monitored my temps and they never got above 48C... I guess I may need to re-seat my aftermarket GPU cooler.. although my GPU temp monitor never went over 55C

Oh well, I guess i\'ll just keep it at stock and live with it