1. First, download the XViD QuickTime Component (make sure you get the Intel version, at the bottom of the list), then place the component files into your Library/Quicktime folder (can be either the root HD folder or your Home Library folder, but you will need admin rights to place it in the root Library folder)
2. Download the AC3 Codec, again making sure you get the Intel version (at bottom of page). Again, place the component file into Library/Quicktime folder.
3. XViD movies should now play though Quicktime. Place in your Movies folder to see the files in the Videos > Movies section of Front Row.
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