I started several projects in Windows Movie Maker version 2012 (build 16.4.3528.0331) on Windows 8.1. I imported 1-2 video files per project, where the video files were in a direct subdirectory of the project directory. I waited until WMM finished with "Movie Maker is preparing your files"; then I saved each project.

Then I decided to move my video files to be in the same directory as the project file (the subdirectory name was a meaningless artifact from the camcorder). I renamed and moved the file(s), then edited the .wlmp file with Notepad to change the absolute path to the video file to its new location.

I opened the project; but WMM again said "Movie Maker is preparing your files"! Why?

What is the recommended way to organize files (project, video and photo) to allow me to move them all together to a new directory without having to re-prepare all the files?