Re: "What about taking an external USB 3.5" floppy drive and connecting a 5.25" drive to the interface that is being used for the 3.5" drive? It seems like it should work." Won't work. ALL of the USB 3.5" floppy drives that I've taken apart (over 100) are fully integrated USB devices. They are NOT a standard floppy drive (with a 34-pin floppy drive interface) and a USB-to-floppy controller.