If you are refering to the internal microphone on your computer then try this. Open up your windows sound recorder from Start - Program - Accesories - Entertainment
. Hit the record button and talk or yell something if you would like. You should see recorded sound waves in the middle of your sound recorder. If you do not see the recorded waves this might mean that your microphone
is turned off. To turn it on just Double click on the little speaker icon on your taskbar at the bottom right of your screen. The volume control window will open. Click on options then properties. Next check the small round recording button. Now make sure the microphone box is checked then click ok. Now a window will open that will show your microphone recording level. Move the slider up about half way and make sure to check the small "Select" box near the bottom of the slider. Open up sound recorder and try to record again. If this does not work your internal microphone may not be working or your computer may not have come with a built in microphone.There are some very cheap external mics on the market that sound very good. If you are doing any serius recording you may want to invest
in a USB microphone. The USB mic should come with it's own software
and setup should be pretty simple. I hope I have been helpful.