Is it a name brand PC: HP, Dell. etc.? If not, then do you have an add-in sound card, or is the sound on the mother board? Look at the sound connection to see. Now open up the PC and look for either the sound card model or the mother board model.
Now you have all you need to search for a driver, either at the PC site (for HP, Dell, etc.), the sound card site, or the mother board site.
If you are still having problems locating the driver post the info above for help.