Well now just because you think it is a dual jack, doesn't actually mean it is. Many laptops don't have them anymore. They have just output ones (for headphones/speakers) and don't work for any inputs. A good way to check would be to try any other 'input' device.
Also you can try the following and see if you can get it to be recognized. But honestly it sounds like your jack isn't made for mic usage.
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".