Then playing game XPSP3, after 10-15min computer do restart.How so

[Gameslove]

Then playing game Windows XP Pro SP3 32bit, after 10-15 min computer do
restart. How solve? I haven't this problems on Vista SP1 32 bit.

My PC:
Intel Pentium 4 (640) 3200@3525Mhz
Zalman CPU Cooler CNPS9500 LED
Abit i945P (AL8/AL8-V(LakePort-P)) Audio 8 ch
2 Gb DDR2 533Mhz Dual Channel (A-DATA 2 x 512Mb + Apacer AM1 1Gb)
Giga Byte Radeon HD4850, 512MB, 256bit No OC (stock cooler)

 

[Bob I]

Event viewer have any clues as to restart cause?