What do you mean by it won't let you launch it? the Limewire media player won't play video, but they should launch in your default media player. Usually if a video file won't play it is because you missing the proper codecs to play it.
XP Codec Pack 1.3.0 Is a good one for Windows media player. Be sure to install it if you d/l it.
You may want to try playing it in a different media player.
VLC media player is a good one that has the codecs built in and will play most types of files.
This thread has a lot of good info:
CODECs list for Movies /Alternate players / Video help forums
Some files are bad/corrupt.
Bitzi Web Lookup is a way to help sort out which files are good or not.
For help on setting default apps:
Setting Default video app
Hope this helps
