Whenever I attempt to extract .zip files containing 1980s old Dos games to a folder on my external hard drive, I get a message in the action center that reads, "back up your file encryption key" and all the file names of the extracted files and folders are in a green color. A search on the internet brings up stuff about encrypting a whole file system. Adding .zip to the search doesn't bring up anything useful or related at all.
What is this message and how do I avoid it in the future?
Please and thanks