A school teacher at a small charter school, teaching various levels of math and a few foreign languages. This person was pretty technically proficient - they used a linux to access the web, but it was set up to boot a browser in to full-screen kiosk mode, and they pretty much just searched webpages and printed things out sometimes, no email really.

The DOS was DRDOS 7.22, and it was very elaborately set up -- it boots from a CDROM or USB flash disk as a live disk. On the disk is every assignment, homework, or test for any of the various courses he taught, carefully organized. They are in WordPerfect 5.1 with a few graphics in another program, and a graphing ( as in X-Y cartesian plots ) program also, all ancient freeware DOS. The three programs come up instantly on boot in different terminate-and-stay-resident screens, that you switch to with a control-alt combo, very like switching terminals in text mode linux.

This meant he could take a CDROM to school, pop it in the horibly slow and ad-laden windows computer some government program had given the school for free, boot, disconnect the printer from the network to the constarnation of other teachers and plug in a USB cable, and print his assignments, and never bring back viruses. The students when they learned of this situation would search out old viruses on the web and try to infect everything.

But using windows and mac was pretty limited to a little bit of browsing, and occasionally going to a dedicated machine with the right program already set up, to enter grades and time sheets and etc.