Graham,

I have operated an HP laptop very much like yours with Ubuntu (desktop version), and it performed flawlessly with both audio and video.
Very likely, the Linux audio drivers that run your soundcard need to be adjusted. The Ubuntu forums are your best resource - very few people on this forum can help you, because PG Music software is not compatible with Linux.

This thread will get you the information you need:
Ubuntu audio


just looking for clues...
Oren.
http://www.masteringmatters.com