The only thing I can tell you is to uninstall the drivers. Then run one of those registry cleaners like CCleaner so it will delete the residue from the REGISTRY. Next look in the hardware list for the sound device...if still listed after uninstalling and then delete it from the list. Reboot and Windows will detect it as new hardware...from there it will of course try to install drivers on its own...that's when you redirect it to the official drivers for your hardware.
That's all I can tell you would normally work for me. If you have the original system drivers...I'd go with those then do an update.
good luck
ps: once you get it fixed...i strongly recommend you use one of those driver back up software programs...I do that myself because they will allow you to reinstall previous drivers rather than do an entire system restore.