CaSaKe

Got a strange problem here
My system sounds when i plug in a usb device ect.. dont work
in some games the sound is completely gone in other games it works perfectly
if i play a mp3 file i can hear the music
i reinstalled my sound drivers but that had no effect
so im pretty sure its a setting somewhere

if any1 has a solution to this or some helpfull info in finding the problem
i'd apreciate it