PC turning off randomly

[YU22]

My cousins pc had started turning it self off randomly 2 weeks ago, it happens from few minuts to 1/2 hour after he starts it. It does so in XP, 98 and even if he goes into bios and waits there. Does any have a clue why?

His pc:
Chieftec DX-01B-D Dragon Super MidiTower Black 300W ATX (AMD&P4 OK)
Abit KR7A KT266A 6PCI 1AGP 4DDR-DIMM UDMA100 SocketA ATX
AMD Athlon XP 1600+ Palomino
Maxtor DiamondMax D540X 60.0Gb 5400rpm UDMA100 IDE
LITE-ON LTR-24102B CD-RW 24x10x40x
Gainward GeForce3 Ti/450 TV Golden Sample 64Mb 4.5ns DDR TV-out AGP
Creative SoundBlaster Live! Player 5.1 bulk PCI
SureCom 10/100Mbit TP Fast Ethernet Retail PCI
Keytronic Phoenix KT1000 svenskt PS/2
Microsoft IntelliMouse Explorer optisk bulk PS/2&USB
Samtron 96P 19" TCO99

 

[SillyMan]

try switching out the ram it is the problem most times

 

[DaiShan]

I would try running memtest86 on it, but also, it could be the PSU going, does it reboot, or just shutdown? Do you ever smell a burning smell? is the fan on the PSU spinning?

 

[YU22]

It shuts down, power light is stil on but no matter what he does he can't bring it back to normal function. No burning smell, don't know about fan, I will ask.

 

[amdskip]

check out the bios to see if something is making the computer hibernate, what about a heat problem?