I see that your Laptop was not pre-installed with XP, it was with Vista. Installing XP on it, will be a downgrade which is not recommended by them (HP). In HP Laptops, there is always trouble making the device and drivers work with retail version OS.
Anyways, I got the audio driver for XP, you can give it a try....
The Audio is a High definition Audio and we can not install the Audio driver ditectly without installing the UAA (Universal Audio Architecture) driver in Windows XP. So, first install UAA driver (restart) then install Audio driver (restart).
UAA driver:
ftp://ftp.hp.com/pub/softpaq/sp33501-34000/sp33566.exe
Audio driver:
ftp://ftp.hp.com/pub/softpaq/sp32501-33000/sp32864.exe
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