For those who often use Movie Maker, you have suffered the "Insufficient Memory" problem. I finally found the easiest solution. Movie Maker places temporary (Temp) cache files in a unique folder location where "Disk Cleanup" cannot retrieve them in order to delete them. They build up using all RAM and Cache memory, especially when editing a large number of files or large film files. Follow the program pathway and simply delete those "Temp" files yourself and restore your memory back to its operating capacity. Here's the folder to locate and remove the "Temp" files.

C:\Users\(username)\AppData\Local\Temp

Good Luck!