Can you play some time after you've started your computer and then it crashes? That would make me think of a heat-problem. Despite it's looks the S&M games aren't that light on resources btw.
A reboot should leave an event-log entry, do you have 'reboot immediatly on crash' set to on (assuming you run XP) ? Either way, event log should have some entry at least. Reboot doesn't make me think of the game, but more of the driver .. on ATI sometimes an older driver seems to help?