Just a quick note, since I just found out how to get sound working on my HP DV7 (running Ubuntu 11.10 64bit).
Add the following as the last row of /etc/modprobe.d/alsa-base.conf;
options snd-hda-intel enable_msi=1 model=hp-dv5
Then, to test it, run;
sudo alsa force-reload
Now sound’s working. Lovely!