Where are you looking to see if the mic is recognized? It won't show up in Device Manager. Does it show up in the sound devices under Recording?
It could be that the built-in mic failed. Is there a jack for an external mic? If so, I'd plug a mic in there to see if that works.
There is probably a switch built in to the external jack that disconnects the internal mic when an external is plugged in and the contacts on that could have oxidized. If that's the case you may need to open the laptop and see if you can get a piece of emery cloth between those contacts to clean them. If the jack is enclosed, it might require the jack to be replaced.
Edited by strolln, 16 June 2010 - 11:47 AM.