Hello, I had edited a 50 minute film on Movie Maker, but on rendering, I kept getting the error 0x87260103:

"There are missing or unsuable files in your Movie Maker project that are preventing your movie from being saved. Please check that file preparation is enabled in Options, or remove the files and try again."

The strange thing was that the error showed up at about 45% of the rendering, and afterwards it put an exclamation mark on a video that I used 45% through, but also several times before, so it didn't make sense that all of a sudden it was lost.

I looked for almost all the possible solutions, and in short different things work for different people, e.g. updating graphics card drivers, installing missing codecs, re-encoding the file (or all of them) with a standard codec. But nothing workerd, I even tried importing the project file to another editing program to export that way, but the import wasn't perfect.

That's when I found a few people reporting that sometimes, the error is a "red herring" and the issue is not with the files themselves, but with the limited resources of the specific computer trying to render. So, the longer and more complicated the project file and the more low-end the PC, the more likely that this error showed up. Some people solved the error just by transfering the project and its files to a more high-end PC.

HOW I SOLVED IT:

Just by splitting the project to more little projects to use less resources. The number of them depends on when your error comes through, in my case, 2 projects would correspond to 50%, but I got an error on 45%, so I made 3 projects.

Then, render your projects seperately. In my case, I was then able to to put these 3 files in a new project, and render it without problems (I assume it took less resources that way).

But keep in mind that with every rendering and re-encoding of your videos, the quality decreases. So the optimal way is to join the seperate files with a utility like FFmpeg concat demuxer (info on how to open the Command Prompt here and FFmpeg download URL here).

Best of luck, and in general avoid Movie Maker for long projects, it's not suitable and it was discontinued in 2012.