Your probably trying to download
fake files. Check them with
Bitzi Web Lookup before downloading. Also if you do a search and get over #1000 sources then they're are most likely fake, though there might be a good file or two sprinkled in. Try the files with the least #of hosts and with a modem speed. This will help improve your chances.
More tips in this thread:
How to find music(also applies to movies).