Check if the microphone options have been activated in the audio options. First thing to do is to go to the Control Panel and go to the Voice tab Test the hardware. If the hardware still does not work, you can choose the option to check the manufacturer's model of the laptop and refer to their website for these type of problems.
My microphone was apparently "currently unavailable" so I tried to figure out why. I realized it was because I didn't restart my computer after it updated. I have a HP Pavilion g7 with Windows 8. I'm not sure if it applies to all Windows types but it's worth a try. Basically go to where you have your system updates, and see if you need to restart your computer. For Windows 8, you go to PC Settings and go down to Windows Update. Then you press Restart Now. After it's finished, your microphone should be working.