I checked that mobo on HP/Compaq.
They do not list XP 64 as a supported OS for the Softpaq that contains the audio driver. That doesn't have to mean anything. On-board audio (which alot of those computers use) chipsets are made by others. Can you find out what the chipset is for your audio? -Is it Realtek, Silicon Image, etc? You can find out by running msinfo32.exe or one of the third-party system analyzers (Sandra, Belarc). The info *might* be in a manual somewhere, but I doubt it.
Anyway, if you can find out what the chipset is, search for a driver using that angle: Google: "Realtek ALC8190 Driver XP 64".
Betcha find something...