Which version of media player do you have? LabVIEW (6.1, 7.0, and 7.1) doesn't work with media player 9.0.
<a href="http://digital.ni.com/public.nsf/websearch/5EBD67575DD88DD186256E8B0050453E?OpenDocument";>Windows Media Player 9 ActiveX Container Does Not Display Video in LabVIEW Front Panel</a> Zvezdana S.
