Out of curiosity I dug out my old Sony Vaio USB 3.5" Floppy Disk Drive (model PCGA-UFD5) and tried it out.
With the CnM book switched on I plugged it in, without a floppy in I got the USB icon with a cross in it.
Again with the machine on, I put a floppy in and plugged it in, and got access to the files on the floppy disk.
Removing the disk and inserting a different one did nothing, the list of files remained as per the original floppy, even with a re-scan in mc, hence a 1.44MB HDD, just like a HDD I would have to unmount the USB device and remount it with the new disk in.
I hope this info may be of use to someone, lol.
Cheers
