Open the volume control by right clicking on the speaker icon in your system tray and choose open volume control (if you have soundmax audio then the procedure is different). go to options>properties, and select "recording" in the radio button. Click on the select button below the microphone slider and increase volume until it works. Note: to hear the sound from your speakers when you speak, you will have to unmute microphone from the "playback" window.
Hope this helps