If the video plays in Windows Media Player, but it does not play in the ActiveX Control, then you either have an old version of Windows Media Player, or a corrupted control. If it doesn't play in either Windows Media Player on its own or in LabVIEW then you have missing codecs. You did not indicate which version of Windows Media Player you have.
You could try reinstalling Windows Media Player.
You could also try a different player. Many people have successfully used VLC.
