I would go into "Control Panel/Device Manager/Sound, video and game controllers" and uninstall the sound card or onboard sound. Tell it to remove the drivers if it asks. Reboot and let XP reinstall any way it wants to. If that didn't work, I'd find drivers on line from the manufacturer and download them, then remove whatever drivers I had and let the driver installer do its thing. If there is no installer in the package, or that didn't work, either, I'd remove everything again and reboot, and when Windows asks, I'd point it to the drivers I'd downloaded. If that didn't work I'd post here again.
P.S.--Be online when you let XP search for drivers.