If your microphone isn't working, try the following...
- Go to "Control Panel".
- Click on "Sound".
- Click the "Recording" tab.
- Click on the device you are trying to fix.
- Now click the "Configure" button and then click "Set up Microphone".
- Once that is complete, click the "Properties" button.
- When you are done with your changes, in "Properties", click "Apply" and then "OK".
- Then click "OK", again, on the main "Sound window".
NOTE: If you don't see the microphone listed (which would be odd) then right click on the white/empty background of that window and make sure both show disabled and show disconnected are checked.
If the microphone is there but grayed out, then you may well have a damaged device.