Well since your talking about games here, what games are you playing? (Need to know if they are too advance for your graphics card.) Also did you update your graphics card from Nvidia?
All the games i ever played (farcry, need for speed, half-life, halo, resident evil, rollercoster tycoon, etc) all all have hanged while playing.
The computer just hangs without any warning. keyboard, mouse, speakers, and the whole computer hangs. but the fan is still running. i have updated the whole computer drivers. just a week brfore writing this. and i had that problem before updating also. i had ran full virus scan from norton-antivirus 2005, hijackthis, spyware doctor, XoftSpySE, and many more nothing appeared.