The thing is, I am able to (supposedly) make the images myself using disks I know that boot the Mac. It still doesn't seem to make a difference. When I mount the disk in 7.6.1, I'm able to access and read from the disk just fine (which is strange).

I have quite a few 400k/800k DD disks lying around (no disks purely marked as 400k, however), and I even tried to write to one of the disks that I knew had a working system on it, and writing to that disk gave me a nice coaster.

I'll read more about disk images, thanks. PowerPup, I will also try again with the disk images using those tools, thanks