I have asus a7v266-c with integrated c-media something soundchip.
(I've mentioned this in many threads, but I'll ask the question here, before I go get myself a real mobo with realtek soundchip

)
The problem with it is, that it doesn't work correctly. When I play mp3's, it cracks and hisses every now and then as if it can't process the soundstream quickly enough.
In games, it seems to make the fps drop to 1 every three seconds for a short while, after which it catches the fps again.
It's very annoying.
The latest driver from asus is dated somewhere in 2002. My first attempt to fix the problem would be to update the drivers, but alas, there aren't any.