Hi. First, let me say that I am SO not technical. So, please dumb-down any explanations offered. I have a My Book for Mac (not sure if 2TB or 3TB - can’t find on unit) that I have been using for years, to store pics and video. My MacBook Pro OS is High Sierra. Today, I tried to open some movies I made in iMovie (several years ago) and had stored on My Book. Instead of having the original extension, for some reason they now have .rcproject extension and I can’t open them. I dragged one of them to my desktop and just changed the extension to .mov and it will play. But, when I try that with the others, it doesn’t work. What would have caused the iMovie extension to be changed, after several years? Would it have something to do with updating my OS? Should I be updating My Book for Mac every time I update my Mac OS? I really hate this because I spent many hours making those movies in iMovie. Please help!? Thanks in advance.