Something is screwey with this built in sound card in general, but to get the mic to work in Dapper, do this.
At the very bottom of /etc/modprobe.d/alsa-base add
#Low mic fix
options snd-hda-intel model=ref
Then reboot. The Mic jack will work. I think the laptop has a built in mic, but I don't know where it's hiding.
testing
-- PorchLight - 20 Aug 2007