I assume your using XP or Vista?
Unmute your mic in sound. With XP its a gray speaker on your toolbar click properties and hit "mic" then it should pop a mic box with mute under it.
With Vista it will depend on your onboard sound or soundcard but go to Control Panel - Sound - Recording - Levels - 100% mic (make sure its not muted too)
Then set your mic to +10dB (can lower if its to loud) then go to Enhancements DC offset checked and Noise Suppression check.
If you use a soundcard you should know by now how to use it...if you use Realtek make sure to boot the realktek software up and manage it there under Microphone settings.
I find this works for most people. Also I have NEVER had issues after doing this with ANY VOIP software on any game. I never even had to touch my AA3 settings (cept to make sure push 2 talk was on)