please give us more details on your problem. just saying you lost sound is that not helpful. when you try to play music does it give you an error that no audio devices are installed?
did the ausio used to play okay and then suddenly it quit on you? do your audio players (windows media player, winamp, real player, ect) seem to be playing the sound file but you are getting no sound from your speakers or headphones?
if it seems like it is playing than you have a software configuration problem. if you get no device error than you may have a hardware error, unless you have not installed the correct drivers.
double check all the basic things like if your speakers are connected properly and in the control panel you have the sound levels turned up.