cannot adjust webcam mic

I'm using the vx6000 microsoft lifecam with WLMessenger and xp pro;

I get picture and sound from the person I'm calling, and they (sometimes)
get my picture--but sound comes through as just noise.

When I go to Messenger/Adjust Audio Video, it recognizes my speakers, but
when I go to next screen to adjust microphone level, the slider refuses to
stay put--you put it up and it sliiiiides down. Cannot get VU meter
(green/yellow/red bars) to respond. I'm guessing this is where the audio
connection problem is coming from , but don't have a clue as to how to fix
it.

For one bizarre moment, after I checked the "use headphones box" in the
speakers page(even tho I don't use headphones), the slider stuck and the vu
bars worked, but after those few seconds, I could never get it to repeat.

Help would be much appreciated.