I've Windows XP Prof. and i'm using M-audio Audiophile 2496 soundcard. My MSN Messenger-, Windows-, some game-, windvd sounds won't work, i don't hear them. And some of my mp3s i don't hear example Solo Guitar. If i'm trying change example M-audio Delta AP Multi to M-audio Delta AP 1/2, so it move it back, even if i deactive that 'known thing'. I've tried delete and got new drivers, but that's not helped. Once i remember the all sounds worked fine, but sometimes i lost the sounds that db is 0. I can't change any properties, because it moves them back. Like an undo.
try uninstalling your sound cards drivers and installing the latest ones found here http://www.m-audio.com/index.php?do=support.drivers
