What is the problem? Do you get any sound at all?
If not, I guess you don't have the drivers for your sound card installed. If you know the model of your sound card just go to the manufacturer's support web page and download the appropriate drivers.
If you don't know what sound card you have, you can find out this way:
Look in Device Manager, or Start > Run > dxdiag > Sound tab
or
Download Everest Free Edition and go to Computer > Summary > Multimedia Audio Adapter where you will find the make/model and a link to the latest drivers.