Can I just discard any movie that might or might not exist and how?
I am not sure there is a movie on this computer; can I discard it if there is one?
iMac 21.5″, macOS 10.15
Well, you certainly can't delete things that don't exist. You also can't delete things until you can find them. So, step one would be to determine if there is anything on your computer that you want to delete. Then, drag it to the trash.