Re: NT
"21 3.5" disks, and the installer insisted on *every single one*."
I don't remember what Xenix used but I don't think it was quite that many.
I had a SCO install which came on a CD but needed a sloppy to boot. It wouldn't install on Virtual box even if you could get a copy of the floppy onto it - it didn't like the emulation. I had a few clients with Informix on SCO (the staple of a lot of small businesses at one time) so having that on a laptop was quite useful. About the time laptops no longer had floppies Linux became mature enough to use without spending more time fiddling with it than doing actual work (KDE 5 is making me start thinking that things are going backwards).