First, open the volume controls. Find the volume control icon in the system tray:
and right-click on it:
Click on "Open Volume Controls":
Next, click on "Options":
and click on "Properties":
Click on "Recording", then click on "OK":
Make sure there is a checkmark in the "Select" box for the microphone, and adjust the slider to get a good volume. Also, click on "Advanced":
Make sure that there is a check mark beside "20 dB boost". Note that not all sound cards make this option available.