I ran Windows 2000 from the last beta until they stopped supporting it. The only thing I ever loved more were my Commodore 64, my Amiga 500 and Blue/White G3 tower running Mac OS and Mac OS X. It was extremely consistent in terms of UX, more so than Windows 98 that had all kinds of 16-bit cruft left in it.

It did not use a lot of resources, I was a bit of a tweaker back then and I just shut down any services I didn't need for home use and it was absolutely fine on 64MB.

It ran all games and applications that I tried to run.

I HATED the Windows XP UI, never installed it. Why install something slower and uglier? 2000 was way better out of the box without ever experiencing issues in terms of compatibility.

It's true Vista had a ton of nice new features under the hood, but the inconsistency in terms of UX of every Windows version after 2000 felt extremely off-putting.