Games Crashing The PC?

I'm playing,Then my screen Goes blank, I Hear my Fan go Full speed, Then My computer reboots, But It's stuck at "Starting Windows". I decide that a system restore is my only option, So I go with that Right, So my Brand-Spanking New Copy Of Halo 2 Arrives. Boy am I excited, I suspect that after MS Shut down Original XBL, The PC Community will recive a much needed Boost. I don't activate my copy yet, I just want to play some campaign First. I load up the armory, And just as you get out of the tram-thing with johnson, I hear Lots of Sound Glitches, And the same thing as before. It does it a few more times. Then I played some DiRT 2 about 20 minute's ago, It it does the same thing.Now, I suspect It's only Games For Windows LIVE (GFWL) Games doing it, But then I remember that CoD4 did it. Now I'm afraid that if I play anymore games, And do this too much, That I will Seriously Screw My computer.