Is the multimedia card built in to the motherboard or is a seperate piece of hardware? When you go to device manager can you tell me which category it falls under if there is a ? or a ! mark next to the hardware? IE: if it falls under computers, disk drives, display adapters etc.
What you can do is if you are reinstalling windows xp, perform a windows update and from there instead of choosing a express update choose custom update. On your left hand side it will have a option to see if there are any hardware update you can perform. Let me know if this helps