During some games, my computer will reboot for no reason (well, there's most likely a reason, but I've no clue). Sometimes it happens as soon as I load into a level in the game (Brood War), or sometimes it will happen randomly in the middle of a game (Alice, Postal 2, Splinter Cell: PT).
I have a NVidia Geforce FX5200, I just updated the drivers and continue to have the rebooting during games. I've taken a screenshot of the error details I get once the computer restarts.