If I had to guess at it, I'd say you weren't recording the microphone. You're recording "Everything on the Computer." That's why the sound only shows up after the microphone has been into the computer and on the way out again.
-- When you reinstalled Audacity, it should have asked you in the process if you wanted to reset the Preferences and Settings. Say yes, otherwise old settings will hang around and possibly create problems.
-- Do you like to record YouTube performances and music? Those are the settings which can do things like this.
-- Audacity checks for connections when it starts. So connect the microphone, let Windows find it and only then start Audacity. You can also Transport > Rescan.
--Your microphone should appear in Windows settings and the little Win7 sound meters should bounce when you talk.
-- Your microphone should appear in the Audacity Device Toolbar.http://manual.audacityteam.org/man/device_toolbar.html