Not a good idea to launch anything except music & video from LW. The media player only plays music! Open these other files separately using your other apps. If you're having probs with watching you videos, then you need to have a default video player & codecs so it can play the particular type of video it is. Try VLC (it has built in codecs & is free):
http://www.videolan.org/vlc/ (use any mirror dwnld link) & make it your default video player. Alternatively dwnld xtra codecs for whatever player you already have:
http://www.free-codecs.com/