Have Sound Output but No Sound Input???

I regularly use Ventrilo and Teamspeak for gaming online. Last night when I plugged in my headset I could hear eveything fine as always but the mic did not work. All the settings and everything are the exact same as when it was working last week, and I am using the on board sound. (Legacy/Vinyl AC'97) drivers. I have tried to reinstall the drivers and made sure that nothing is muted. The only thing I can remember that I have done differently since last week is install CA anti-virus software (No firewall is on), Warhammer Online, and yahoo messenger.

Oh yeah, I also tried to use the Windows sound recorder and even ith everything turned all the way up it didn't so much as pick up a death metal style scream into the mic.

I am completetly dumbfounded by this and would deeply apprecite any and all help someone could give me. Thanks ^_^