Check your process list in task manager and kill any process that looks suspicious... but don't kill any ati drivers ;)

Man having such a great system and not being able to play doom 3 much suck bad

Anyway... did you overclock your cpu or graphics card that might make it crash ?

Check bios settings, check memory ;) lol

No seriously... what is your sound card ?

Try updating sound drivers...

Try disabling sound blaster to see if that's the problem.