Make sure al the wiring are in its place.
Did you uncheck the mute check box from the volume control (control the settings on particular channel/s)?
CONTROL PANEL -
SOUND, SPEECH and AUDIO DEVICES -
SOUND and AUDIO DEVICES -
ADVANCE on Device Volume -
uncheck mute on Microphone -
ADVANCE on Microphone Check on 1 Mic Boost
Make sure your Sound Manager (control the settings of the sound processor) is setup correctly too.