iVI checks the extension of a file name (the .mod or .mp4 bit at the end) in order to see if it's a file type that iVI knows it can convert. If it isn't a known extension then iVI will not accept the drop of the file. However, iVI can convert many more file types than we check and so if you're sure the file is a video file then you can add it to the list that iVI can accept. You do this by entering the extension on the General tab of iVI's preference in the Allow files with these additional extensions to be dropped on iVI box. Just type the extension of the file followed by a comma and it will be added to the list. Then you should be able to drop the file into iVI's main window.