magicer ,u have a faked up OS!
u see ,i had the same problem and lets review it:
1) inlobby u have sound
2)playing music/movies or other shit ,plays well
3) ingame ,u have no sound
4)ingame when u die ,u hear the whining sound that u die(that is the only sound u hear)
5) Once out the game u can hear the music inlobby!
Well ,if that is so ,i've tryed everything possible same as u did!
Reinstalling my sound card ,reinst crossfire ,clean registry ,EVERYTHING i did was in vane!
I resolved it by reinstalling my win xp sp3 ,than it worked!
it work today also but i had like a month or so without sound just like u!