My brother's PC keeps turning off when playing games. I suggested he has a faulty PSU, it certainly has a high enough WATT rating to power the PC. I was just wondering does anyone else know of any possible causes before he forks out on a new PSU?
Thanks.Could be overheating, download speedfan and post your temps....has the pc been cleaned with compressed air recently?...are your fans all RUNNING?
Swap in a known good power supply and ELIMINATE it as a cause.
Reseat your ram as well.

http://www.almico.com/speedfan.phpThanks Karnac.
He used speed fan and cpu-z to monitor temperature on the GPU and CPU over a few days, there were no temperature spikes around the crashes. And he hasn't been in the PC to clean it or anything. When it started happening, at the beginning of summer (which made him think it was overheating, apparently not) he rebuilt the PC completely and it still crashes.
He thinks it may be an issue with GFX card firmware (ATi HD 4870). He has tried uninstalling it and re-installing it PLUS drivers to no effect. He is now going to remove the card, boot in safe mode, uninstall, remove all drivers and registry entries and then reinstall the lot...

He also ran a stress test on his card which didn't cause a crash, so it's crashing while playing games but a stress test didn't crash it, plus it isn't getting very hot....
I'll tell him to see if he can get his hands on a different PSU to test to see if it's that, but I'm sure he would have tried that if he had a spare.
Any thoughts in the mean time would be helpful
Thanks

P.S When I SAY 'crash' I mean turns off.Try the different psu.  When you remove the card switch to onboard video in bios and run like that for a while to see if it improves....then you can narrow it down to the card....Have you had any other power symptoms like random reboots or freezes....Have to ask....was thermal paste reapplied during the upgrade?....Still leaning towards the PSU.....Seems like the card is tapping the power supply when the games are run and the psu can't handle the power demands.I AGREE with you Karnac about the PSU, however it is a new PSU, only about a year old. I don't know the Watt rating of it, but I can check it out when he gets back online... I'm sure it's got to be atleast 300w, which should be more than enough to run any combination of components, should it not?
Therefore perhaps it is faulty... I guess their isn't anything more to try without a different PSU.
I'm not sure whether he used thermal grease but looks like the heat sinks are doing their job fine if speedfan isn't reporting any high temps, right?
Thanks for all your help. He could take the side off the case and run the games with a table fan blowing into the case....might bring down card temp and give an indication of whether heat is the issue.....300 watts should be good...

Should have asked this first post......how about the specs for his computer....how much ram in there? If its 300w its your psu.  A 4870 and a 300w psu will not work