If your microphone isn't working, try the following...
1. Go to "Control Panel".
2. Click on "Sound".
3. Click the "Recording" tab.
4. Click on the device you are trying to fix.
5. Now click the "Configure" button and then click "Set up Microphone".
6. Once that is complete, click the "Properties" button.
7. When you are done with your changes, in "Properties", click "Apply" and then "OK".
8. Then click "OK", again, on the main "Sound window".
NOTE: If the 3.5mm jack you are trying to use it in is actually an output one, and not an input one, then there is no way to fix that. To use the microphone you would need to get a 3.5mm to USB adapter to use it.