Saving files in Windows Live Movie Maker is slightly more complicated than in other applications. If you are not finished with your movie, you should save your project as a .wlmp file. This type of file can only be opened in Movie Maker. To use this method of saving, simply go to the backstage and click "Save project" or "Save project as." Save project as simply allows you to save a different version while Save project just overwrites the current project file. You can also save using the keyboard shortcut ctrl+S.
If you save it as a movie, it becomes a video file, which is smaller than a project file. Once it is saved as a movie however, all transitions and effects become permanent. The only way you can make a change to it is if you import the file into a new project. To save a project as a movie, just hover the mouse over "Save movie" and select the best setting for your movie. We recommend keeping a copy of the .wlmp file just in case you need to make any changes later.