Hi, welcome to the Magix forums.

First, please read this post and give us ALL the information requested there. At the moment we know nothing about your computer and almost nothing about the actual software you are using, especially the version (check under Help>About...) and variant.

You mention a "mod" video; did you mean "mov"? In which case, that is a format that requires Quicktime to be able to play it properly. Does the file play properly in any other player on your computer?

It would also be helpful if you would download and install the free MediaInfo, point it to your file and post the results of the Tree view here.

Jeff