Multimedia audio controller-no sound card

[adi]

hi,
I got dad's old pc and the multimedia audio controller wasn't installed properly.
he has xp installed on the computer without the installation cd. he doesn't have a sound card on the computer and he doesn't know the manufacturer of the motherboard. how do i go about to fix this problem? maybe i should install the multimedia audio controller standard from the xp installation cd? how should i do that if i haven't got the cd?
plz, plz, help me!!!!!!