Select the file on your hard drive and use the Finder's Get Info (cmd-I) to bring up the "Open With" options. You can set the default and alternate programs to use for your files there.

These free players can often play video that is a problem for Quicktime
http://www.videolan.org/vlc/download-macosx.html
http://sourceforge.net/project/showf...group_id=62947