MDaemon's UI on Windows Vista operates differently than on other versions of Windows.
Under Vista, MDaemon will run as a service in a hidden window completely inaccessible to the user. This is designed behavior. To configure MDaemon you may log into WebAdmin or use a Configuration Session.
To log into WebAdmin, open http://{IPaddress}:1000 in your browser (where the IPaddress is the IP of the MDaemon server).
To open a MDaemon configuration session, simply log in to the MDaemon server via VNC or Remote Desktop and go to Start | Programs | MDaemon | Start MDaemon.