The thing is SP3 installed the driver. You actually need to go disable it in device manager, then uninstall it and try the reference driver
at Realtek
Alternatively roll back SP3, uninstall the UAA and any other sound devices, then install the HP driver and and the UAA if requested (or just try the realtek reference driver) and then put SP3 back on.
Frankly when dealing with XP, I install with SP2 slipstreamed, get the drivers in, then put SP3 on and then update internet explorer last. Seems to go better that way.