If my memory is right, the Tandy has a DD floppy drive, capacity is 360k. Most "modern" drives are HD, and have capacities of 720k, or 1.2m . The track written by a DD drive is twice as wide as the one written in a HD drive. The Tandy will only be able to read disks formatted in the DD drive, with the wide track. Formatting the disk in a HD drive results in a floppy that can be read in the HD drive, but because of the previous wide track written in the DD drive, DD drives will see a narrow formatted track in the middle of a wide track. Result - read errors. My experience has been that to use a DD floppy, you must format the disks in them, and they should never have been written to or formatted in a HD drive. It's a nightmare I used to fight all the time. I was delighted when the 3-1/2" floppy came out. It didn't have these issues. There is no easy solution. There is a web site that has forums concerning old computers where you might find some information ... www dot vintage-computer dot com. Good luck!