Audio drivers or if you have a soundcard the drivers for that.

To find the drivers go into control panel, add/remove programmes and it should be in the list, just make sure you have the drivers to put back on first, you dont want to uninstall then think shit where do i find the drivers to install you should have discs with your laptop with the drivers on or when you find what drivers they are you could google it and download them from the net.

Not sure if that will work but according to the chap above it does so worth a shot