I have Compaq CQ40-337TU series. It has a problem audio support when you use headphone. The audio won’t go to headphone. Perhaps this works to another Intel series. I use Intel Corporation 82801I (ICH9 Family).

I was add this line on /etc/modprobe.d/alsa-base.conf on my Fedora 12 machine (previous fedora may works too).

options snd-hda-intel model=3stack position_fix=1

options snd-hda-intel enable_msi=1

And restart your laptop. Having fun with your headphone.. :)