Windows XP
When Windows XP first released, people criticized it for having a theme that they hadn’t seen before in Windows. People thought it was very kiddish and appealing to children, not being taken as seriously for the large userbase of the time. There were also criticisms about how fragile Internet Explorer was (I’m not kidding, I was there and Internet Explorer back then was at its most insufferable.).
But these days, just because of how bad Windows 8, 8.1, 10 and now 11 have been, people have praised Windows XP so much.
Similar, but 95 already moved to second partition in 98 or so already.
7 was my last one privately.
Still stuck with W11 at work, but for a large part just use at it as a starting platform for WSL and Virtual Box.