Just a quick note. I had an issue with my new laptop where the mic would not mute no matter what I did. I went to this site and this info helped.

Okay so what’s probably happening is your audio hardware is mixing input from the microphone into the speakers without Vista doing it. Try opening up the sound panel, double-clicking speakers, and checking the levels tab. Is there a microphone volume/mute there?

So I hope that this helps you out if you are looking for a fix to a mic not muting on a laptop with Vista.