Hey Sky,
I found the following about the mci command -
http://forums.speedguide.net/showthread.php?t=167397
http://www.pcreview.co.uk/forums/thread-390284.php
It looks like it can hang things up on shutdown and restarts of your system. If these 2 links don't seem to help, I just put the following into google and it brought up a bunch of stuff - "mci command handling window"
Good luck with it!

sabby