a few days ago, sound stopped working on my laptop.  I'm starting to
suspect that it's a hardware problem, but since I'm not an expert when
it comes to hardware, I'm not sure how to go about proving whether
it's a software or hardware issue.  Can anybody give me any pointers
on where to start looking?  If it were a desktop, I'd just try
swapping in a new sound card, but I'm not sure what to do on a laptop.

The basic symptom is that the music player acts like it's playing
stuff, but no sound comes out, either from the built-in speakers or
the headphone jack.

Does anybody know of a definitive way to prove whether it's a hardware
or software issue?  By the way, I'm running Ubuntu Dapper on a HP
zv6000 series laptop.

Thanks,
Jonathon