I had a couple files on my Elements USB HDD before I flashed batocera to it. Are those files now gone? How do I uninstall Batocera? Is formatting the only option? I didn't realize I wouldn't be able to go into the root of Elements HDD anymore after installing. Thanks for you help.
installing takes a full disk, so yes, data are lost.
uninstall has no meaning, it is like how to change the form of modeling clay : just do an other form. just install something over.