I looked in my control panel and into the Multimedia file - however, I did not see an option for the mic to be muted. Perhaps my computer's setup is different because I have Windows 98? You can choose which device to use (maestro recorder) and if you click advanced properties, 'hardware acceleration' and 'sample rate conversion quality.' If I click on my sounds icon on the lower right corner, I can click on options, for recording. A recording volume does show up, but there too I don't see a mute/unmute option.
Thanks for taking the time to look at this question. I gave up a long time ago so if nothing comes of this it's no big deal.