If you are getting no sound at all, then...
First, check the obvious - are all wires and cables connected & plugged in etc?
If you have a set of headphones that you can plug in to test the output, then check if you have any sound with them.
Open the volume applet up completely so that you see all the sound inputs - is the wav section set too low?
If you have the original drivers, or they are on the Windows CD, then I would try to re-install them. I would uninstall the driver, then restart and load the drivers.
SD