Which operating system are you using: Windows, mac os 8 or 9 or OSX or other?

Go to QuickTimes Preferences. For windows go to menu bar, Edit menu>Preferences. Then open Advanced Tab & press the MIME settings. Make sure they're all ticked. You can update your QT plug-ins & downld 3rd party ones. The ones that aren't on the update page you can find links to here: http://www.gnutellaforums.com/showth...threadid=34705

http://www.gnutellaforums.com/showth...threadid=41739

BTW get VLC as it plays most things & is free. See CODECs list and alternate players for Movies