Understanding source files
Source files are the digital media files (for example, audio and video files) or pictures that you import into your current project.
When you import a video, audio, or picture file, the file remains in the original location from which it was imported. The resulting clip that appears in Windows Movie Maker is a representation of the original source file; it is not a copy of the source file. In other words, if you edit the source file in another program after it is already imported into Windows Movie Maker, the changes that you make to the file automatically appear in Windows Movie Maker and in any Windows Movie Maker projects that include the edited clip. And, if you delete the thumbnail or clip for the file in Windows Movie Maker, the source file still remains unchanged in the original location. To ensure that you can continue to work with a project, avoid renaming, deleting, or moving the original source files.