Problem with game crashing

Ok so after I run the game and I play it, I randomly freeze, then hear a buzzing and a gray screen. I tried everything you normally would

I have had no trouble with any other game I;ve ever played.

I've read some stuff that said ATI Radeon 4600 has some issues with steam. Anyone have any insight. I wanna come back to the game (quit playing forever ago because of this)
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http://us.battle.net/wow/en/character/trollbane/cowmilk/advanced

bump
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http://us.battle.net/wow/en/character/trollbane/cowmilk/advanced