Greetings, Shrdlu.
Welcome to the Gnutella forums!
What you have been downloading are bogus files. In my experience, all MOV files on the net are bogus (but that may not be true for all). Anyway, some tips here:
http://www.gnutellaforums.com/downlo...ad-issues.html Read through the whole page.
To me, WMP, QT, and Winamp are all bloated ware. I highly recommend the free VLC player, which comes with all CODECs installed. (CODECs will otherwise likely be your next problem). If you continue to use your other players, I strongly suggest you set them to not automatically connect to the web.