you can do alot of things...
1. re install your sound card
2. upgrade your sound card
3. if you have desktop speakers, push in the volume thing u turn kus it gets messd up easily on alot of them
4. start>cntrl panel> sound> (makes sure thats up and not muted) >advanced> make sure nothing is muted
5. if ur talking bout media player: View>enhancments>graphic equalizer
6. start>run> type in: dxdiag> go to the tabs that say sound 1 and 2 and make sure they are on
hope that helps