Pretty simple, this happens on almost every game I've tried and sometimes with no game running I hear my PC post and reboot while nothing is going on it and I'm out of the room. This happens while OC'd and defaulted with no OC.
First crash type: Seems like the on-board sound, I have updated drivers, disabled the on-board sound card and tried an Audigy PCIE. Disabling the on-board in the bios actually doesn't stop the sound from coming over the HDMI to my monitor's speakers. The crashes SEEMED to abate with the Audigy in but they came back (like I said I don't know if the on-board was ever truly off as disabling it in the bios lets it still play sound.)
Crash type 2: Computer will (with no programs running and a fresh reboot) reboot itself while I'm not in the room.
Temperatures are under 42 degrees celsius even when OC'd.
Drivers have been updated frequently.