I had a scare where I couldn't find my OS Disks. What I am now doing is a precautionary measure, others may find useful. I am experiencing the battery almost dead, and need to reload the sequencer operating system, regularly. I will get a new battery i the New Year. My goal is for all my disks to contain the OS. I copy the OS disk, then delete all, but the OS, SD60 internal sounds, and the 20 Internal presets. This becomes my Master disk. Instead of formatting a new disk, I copy this master disk onto it. I end up with the OS on each disk, so I don't need to worry. Ralph :-)