[Troubleshooting] Computer shuts down during games, monitors first and then sound

Once I start playing a game everything is fine for a while but after anywhere from half an hour to more than an hour my monitors show nothing from the computer. The lights from the fans are still on and running but other than that the computer becomes unresponsive and I have to reboot.

Took a picture after about half an hour of gaming of temperatures (obviously computer had not gotten hot enough yet to shutdown):

http://imgur.com/9zM7k

Not sure what is the culprit here so any help would be appreciated!