computer crashes while play css

i had a Winfast PX9600gt in my computer and while in css i would be able to play for a good 20 mins. then my computer just turns off. my friend lent me one of his Gcards its a Nvidia 8500gt and it was workin perfectly thought i fixed the problem but it crashed again.

i have all the drivers i need but idk what im supposed to do.

any one know anything?

17 views and no one knows anything. thats lame

Does this only happen in counter strike source? Have you tested if this happens on any other game? It could be your CPU is overheating, or something is.

Maybe conflicting software...?
Try Disk Defraging if you haven't in a long time
Update all drivers
Try setting all the settings on low.
Try closing everything thats unnecessary like msn, internet browsers, hell, even explorer.exe anything thats no use during gameplay.
And see if it runs longer than usual.

I doubt it most of this should fix the problem, but its worth a shot.

__________________
Windows Media Player Instantly opening, Videos running smoothly, CPU doing great, Heatsink small and quiet, no lag [: