To check this open the Audio mixer. This can be done by clicking the small speaker in the System Tray (bottom right of screen).
The Playback mixer will pop up, but we want the Recording mixer, to get this click on the "Options" menu then select "Properties"
When you have done this another windows will pop up. You must click on the dot beside the word "Recording", then click "OK"
After you have done this, the mixer will now show the input levels instead of the output levels. Now you have to make sure that the slider is pulled up on the microphone control, and that there is a check mark in the "Select" box below the slider.