You can format it on a Mac.

You can read and write to it on a Mac.

You can't do squat with it on a PC.

/edit/ so in other words, you need to get the images onto a floppy-equipped Mac.

If the Mac has a superdrive, you can always get the images -exactly- as they came off the net ie don't uncompress or anything - stick them on a 1.4MB floppy and transfer them across to the Mac's HD, then decompress them there to make 800k floppies