Mic problem

[KweLi]

Ok, so suddenly my mic just stopped working. No one can hear me on vent. I've googled of course, tried doing a system restore, changing ports, updating drivers, changing mics, almost everything. But now for some reason, my mic detects other people talking in vent. I right clicked on my volume icon, recording devices, clicked on microphone, configure, and clicked set up microphone, and when it has that green bar people in vent are talking and its jumping, but when I talk nothing. I even went into sound recording and tried this and it still picked up the people on vent.
I have vista, and its a headset.