You will have to re-install the drivers which should be on the set-up CD for the motherboard etc, or if you don't have the CD, download them from the sound card manufacturers website (usually found in "Support" & "Downloads". A system audit using, say, Belarc will tell you who made your sound card if you don't already know.
I did exactly the same while getting rid of some adware files. ( just knocking out those I didn'r recognise.) Cost me �45 form a mobile PC repairer to get fixed, but it is as Quicksilver says, available as downloads from manufacturers site. keep at it, good luck