Converting .avi files to .mov is very easy with DivX Doctor. All you need to do is to call the application and drag your .avi file to the space. You can add multiple .avi files in one run. Once you have all the files that you wish to convert, all you need to do is press 'Start' and the conversion will begin.
When the conversion is complete, you can then view your .mov files using QuickTime. Just make sure that you have the 3ivx MPEG-4 5.0 codec to avoid any issues. You can download the codec here - http://3ivx.com/download/macos.html
If that codec doesn't work, you may be running MP41 or MP42 video. To download decoders for these formats check out:
MS-MPEG4v1 - http://homepage.mac.com/hmason/mac-ms-mpeg4v1/
MS-MPEG4v2 - http://homepage.mac.com/hmason/mac-ms-mpeg4v2/
For troubleshooting and questions, visit DivX Doctor 2's forum - http://3ivx.com/forum/index.html.