Windows 2000 is the epitome of Windows UI to me, probably because my first PC had Me which borrowed the desktop from it. As i kid I didn't even notice it was different from the 98 machines at school, but when i set up 98SE for retro gaming as an adult I couldn't shake this "something isn't quite how i remember" feeling.

Then i set up 2000 as a server for the retro machines and everything clicked. Kind of amazing how many control panels in Windows 10 and 11 are essentially unchanged from 2000