Comment 19 for bug 153119

I had this problem on my vostro 1500 with fiesty installed but didn't bothered to fix it.
When I installed gusty the sound was gone as well. Fixed the sound with help from this: https://bugs.launchpad.net/dell/+bug/131133. Quite long thread but the solution is more or less install linux-backports-modules-2.6.22-14-generic. Note: it isn't enough with the linux-backports-modules only.

Then to the mic problem that was a easy solution.
Just right cllick on sound icon in to right corner
open edit -> preferences and check everything
playback tab unmute all and raise volume
recording tab unmute all and raise volume
switches tab uncheck everything
options tab choose digital mic 1 as Digital input Source

This works fine for me and as far as I know I don't have a digital mic? I use a koss sb/45 headset.
But still it works for me.

good luck
/Peter