What is is OS? Which laptop are you using?
Generally for a Realtek audio controller, you should see Microphone. Under the properties there is jack information called 'ATAPI Internal ATAPI Jack'. If you can find it, enable the device. If you cant, click 'show disconnected devices' and 'show disabled devices' in the sound-->recording tab (in windows 7).
IF you still cant see any device from the internal jack, then you better re-install the audio drivers or check for the physical connection (highly unlikely cause for this failure).