I would want to share my experience in this. I have a new system motherboard Asus P5GC-MX, with it I installed Windows XP SP1 (my licenced copy) and updated thru internet to SP2 and subsequently to SP3, which was what causing the problem to my Realtek HD Audio driver (later found out). What I did was to Remove SP3 through Control Panel Remove Program. Once removed, I went to look up K888111xpsp2 fix which comes with my MB disk. Then reboot which causes it to "Found New Hardware" and update driver. The file that it is seaching is RTKVHDA.sys which is again on my MB disk - drivers - audio - driver - WDM. After doing all these, I went back on internet and reinstall Windows XP SP3. Hope this could help someone.