Sony readers, properly set up, have a quite elaborate folders system. I just received one with the file system intact, a PRS-950. To work correctly and show up on the menu side loaded files need to be in the correct folders. I now have about 75 photos and 170 ebooks side loaded in it and used it's file structure to rebuild that on another PRS-950 that someone had wiped clean before selling. I described the file structure in the Sony area in the following thread. See post # 97.
https://www.mobileread.com/forums/sh...=293092&page=7