Some computers do not have a built-in microphone.
Have you ever been able t o use the microphone?
Here is some help.
Microphone problems in WINDOWS 8 Notice the above link has several responses from people. It seems some are having microphone problems with Windows 8. The problem often is lack of proper driver for the audio hardware of the computer.
Please provide some detail about your computer. Did it you come with Windows 8 already installed?
Also, Windows 8 has Speech Recognition. Have you ever tried it? If so, that would indicate the microphone is working and your problem is something else.
