I purchesed old desktop model.. asus 2001. its sound system is not working. i dont have mother board key c.d.. on mother board its displayed .....n vidia P5080477 0536A2 S taiwan

Hi,
i hope this helps. since you don't have any idea what your mobo is, it's best to have adiagnostic tool installed (everest ultimate or belarc advisor). you can download them for free inb the internet.it will give you many useful information about your system.
you can also go to your control panel and look for device manager and look for a highlighted device (ususally colored orange or with a question mark) and right click it for properties and look for driver problems. xp will give you suggestions on how to fix it.
finally if the builtin sound is really busted, you can install a seperate pci soundcard and install the soundcard together with the driver oof that souncard if windows does not automatically detect and install that soundcard.