First off, there's some info that's needed.
Did the audio work before? If so, right click My Computer, choose Manage,
select Device Manager on the left, and click the little + next to the Sound,
Video, and Multimedia Controllers entry. Right click and choose properties
of the sound card device, go to the driver tab, and choose "Roll back driver"
If the audio driver has became corrupted, or has never been loaded, we need
to identify the audio hardware that is in that system so we can get you to
downlaod teh proper software from the manufacturer. Is it a name-brand
system (i.e. compaq, Dell, HP, Gateway)? Is it a sound card, or is it
integrated into the motherboard?