Sound cards are dirt cheap.
15$ will get you a card that will do the job.
however, your probably better off looking at your motherboard booklet or reading about your motherboard on the site to find the type of sound it has.
if your board came with a cd, then normally it should come with drivers for it. poke around.
if you know what kind of sound chip you have, then just http://www.google.com/
you should find it.
another place could be www.driverguide.com