xfx oc 8600gt bad or is more power needed?

Hi guys. A bud of mine just upgraded his hp a1130n w/ a xfx oc 8600gt w/ zalman fan, and 2 more gigs of ram (total 3gb now). His psu is stock 300watts. He has a dvd-rw and cd rom drive, media card reader, 250gb hdd, amd 64 3500+. He plays on 1280X764 reso.
The min requirement for 8600gt is 300watts (via tiger direct); however, his card's overclocked. When playing company of heroes ( not sure if only coh); after a while the computer restarts or the screen freezes.
Do you think it's a bad psu, video card etc???
If it is an insufficient power supply, can recommend a power supply that would be enough and fit his case...Thanks.

I had almost the same problem and it was power supply.
Actually the Atx12v 4-pin square cable that goes near processor to motherboard was faulty. It is necessary for additional power.

hey, i've got a 8600GT stock. in my case i had a no name brand 400Watt psu. in silkroad i always got artifacts when the grafics were more demanding. the solution was: i bought a 600WATT and the problem was solved.

I put my money on power supply... a decent QUALITY 450-500w unit shoudl take care of your issue

Help!!!.....put in antec 500w earth??? and still have freezes. pulled out adata 1gb x 2 ddr 400 ram, left the hp ddr400 512mbx2 ram sticks and evrything worked fine!! But then, like a dummy i pulled out the hp ddr 400 ram, placed the adatas in those slots and now having problems booting up xp. CAn't boot in safe mode or last known good configuration either. Took out the adata ram and put back the hp ram and am having the same " no xp boot" problem!!! even w/ the original ram that had worked fine!!! please help!!!