Yesterday I created a movie in Movie Maker and saved it as an mp4. Now, I am trying to open the file in Movie Maker again to add more edits to it. However, there is an error and Movie Maker will not let me open the project as an mp4 in Movie Maker. I then changed the extension to ".wlmp" but it still won't work. Any ideas as to how I can still edit my mp4 file again? Or convert it to an editable file?