Still run windows 2000 at home, although haven’t booted it for quite a while. It’s usable on my eeePC netbook, even in a VM too. Stayed on that version, because you don’t have to do all that registration nonsense every time you reinstall, to prove you’re not a copyright thief.
Do have an XP licence too. No intention whatsoever of upgrading, just to run the windows s/w that already runs on my machines. Why should I?
At work, we only binned some 386’s running DOS6.1 a few years ago (maybe 4-5). We need systems that are stable for 15-20 years, not on M$ upgrade cycles.