iChat Icon   iChat AV says I have a microphone, but I don't

Your computer may have a built-in microphone. Check the documentation that came with your computer.

If your computer has a microphone jack and no microphone is connected to your computer, iChat AV may indicate to others that you have a microphone. To keep iChat AV from indicating that you have a microphone, choose Video > Enable Microphone to remove the checkmark.