Computer and/or Monitor Turns Off During Games

[EwaAzn]

Every time I play any game for my computer, after 10-15 minutes my monitor turns off and my computer like dies but sometimes I can still hear the game music but other times I hear like a buzzing noise. It's a custom built computer that I've had for a year. It's never had this problem before until a few months ago.

Windows Vista
GeForce 9600 GT 512MB PCI-E
2 Gigs Ram
Processor: E8400 3.00 GHz

I've updated my GCard already. I thought it might've been overheating so I already cleaned the fans with compressed air. I don't have this problem with anything else, only when I play games (Sims 3 , Trine, etc. )

I'm really frustrated and upset at this point and I really need help 

Advice?

[Carbon Dudeoxide]

Play the game for about 10 minutes, then post your temperatures.
Retrieving hardware temperatures: http://www.computerhope.com/forum/index.php/topic,83105.0.html