Instruction
1
Consider the most universal and simple way to unmute the microphone, independent of installed drivers and audio card of your computer.

The first paragraph of step instruction for Windows 7, one for Windows XP.

Images are for Windows 7.
Win7:

We find in the tray the loudspeaker icon and click on it right mouse button.
WinXP:

Go to start -> All programs –> accessories –> Entertainment -> Volume control
How to enable internal microphone on laptop
2
In the menu that appears select "Recording devices".
Open "Settings", the select "Properties".
How to enable internal microphone on laptop
3
Find and select by clicking the left mouse button the desired microphone.
Find "Microphone" and put a tick opposite it. OK.
How to enable internal microphone on laptop
4
Click the right mouse button on the microphone and select "Enable".

If the icon has become colored and it did the tick, all is done correctly.
Go to the menu "Volume" (see first step). Looking for the slider under "Microphone", move it to the desired position (adjustable sensitivity of the microphone).
How to enable internal microphone on laptop