Thank you all for the information. Now that I've been educated, I'm in the process of tracking a Mac-compatible one down. This older technology I find, in many ways, more fun and interesting to use than a USB flash drive or the like. Can they be used like a floppy in the sense that I could: pop the MO disk in and save changes to an existing document on the fly? or would I have to have the first erase the disk and then rewrite the file like with CD-RW?