If you have the driver files you can install them manually. Go into the device manager and remove the sound devices (may say unkown).
Then reboot the computer.
As the computer is rebooting an install new hardware wizard should appear if Windows detects the new hardware using this wizard you should be able to point Windows to the folder containing your drivers either on the CD, diskette, or the folder containing the files you downloaded.

--This is assuming you downloaded the XP drivers for your system. Vista drivers will not work for XP.--