The most likely cause is that a recording session is in progress or the MuvAudio Console was never closed.  Please look in your system tray (near the clock in the Windows Start Menu) for the MuvAudio Console icon (music note with a 2 in it).  Either double-click to bring up the console and click "Stop and Exit" or right-click on this icon and click on Exit.  Now open MuvAudio normally and you should get the trial screen where you can register the software.