I have a video file with and ext of .avi. When I try to open this file in QuickTime, I get a message saying some necessary QT software is missing and I am directed to the QT page that lists a bunch of downloadable components. How am I supposed to know which components I am missing? Is there a simpler way to view this .avi file, or better yet, how can I convert the file to a file type recognized by iTunes?