Hm. It may be better to change it to another format - in our previous version of ML, video files are a bit peculiar on what will and what won't run.
The following link may assist in finding video conversion tools:
http://download.cnet.com/1770-20_4-0...form%3DWindows
Also - When working with on-line rating items, don't forget that the item directly after the on-line item will work with the on-line item. For instance, if you want to play a video file with an on-line rating, you will need to declare the on-line rating, and then create a new item beneath it as a 'Movie' type. As far as I know, using the backvideo function with an on-line rating item-type will only cause an error to arise.