HP UPDATE: Well, I finally got to someone at HP last night (my slowness, not theirs) and the computer is on its way back for repairs. They were quite nice. Am I getting special blogger-treatment? Possibly, but I've gotten several emails like this one from Gary Wishon: "My HP laptop was picked up FedEx on Tuesday and I was using it again on Thursday PM. With a follow-up call 2hrs after arrival. I'd buy HP again anytime--and have." And I didn't get any horror stories like I keep hearing about Dell (though I note that my own experiences with Dell have been mostly good). I'll keep you posted.
Meanwhile, I've demoted the HP to family-room duty and done what I've meant to do for a while, putting a dedicated audio PC in the studio. I ordered one of these machines from Sweetwater Sound, and it came today. Had a minor setup glitch, called their support number, and got it taken care of with minimal hassle thanks to a guy named "Mikey." He even gave me some useful advice on configuring my M-Audio interface box with the computer, which is cool. The new computer is much quieter, which is nice.