halo used to make my pc reboot when i quit the game ...turned out to be a compatbility issue with halo and my card....RAD 9000....even though i had the up to datest drivers at the time........3.7s 0r 3.8s.........the issue was only fixed in a later driver release by which time i'd bought a new rig.......might be a driver-card-gamesoftware conflict........thats not been fixed yet by a driver release
dl the forceware drivers from the nvidia site..........uninstall your drivers ........even if they are the same and install your downloads it just might help.
doddsy