Great info here: Are You New To Limewire? Please Read This: Movie download issues
Using LW's link to Bitzi will help to save you from downloading bad copies and infected files.
I recently gave up on WMP and switched to the VLC media player (smaller overhead, more secure, less tempermental).
AVI files seem to be the best, while WMV files are often bogus.
Recently released videos (and probably music, too) seem to have the most bogus files. Best to wait awhile before downloading a copy.
CAM (camera) copies of movies used to be pretty good. Nowadays, any idiot can use a camera, and most do a very poor job.