I guess you're using LW 5.1.2??
Click on Show All (bottom right of the search page). Right click on a movie file > view file info > locate on disk. Now your incomplete folder will open. Right click on the file > open with > choose program. Choose WinAmp from the list & tick the box to always use the selected program > ok.
If you're still having problems with the files after that, try opening them with VLC. It's a free player, has codecs installed to play most file types & is really reliable. If VLC won't play the files then chances are they're bad files. There's a link for download here:
http://www.gnutellaforums.com/tips-t...p3-fixers.html
You can use Bitzi to check files before download. If other users have rated the file, you'll get some idea of it's content & quality:
How to use Bitzi