I turned 18 midway through 1999 and since I was deeply interested in multiprocessor OSes (chiefly, BeOS) I asked for (and was lucky enough to get) a dual PIII-450 system as an 18th birthday/high-school graduation gift.
I dual booted BeOS 5.5 and Windows NT 4.0. Windows 98SE would work, but it didn’t have support for SMP, so one of the processors would be deactivated. On the other hand, it NT 4.0 didn’t support USB, and I had several USB peripherals (my very first digital camera, a Canon IXUS, and a flatbed scanner).
That’s why in June 1999 I joined the Windows 2000 beta programme. It was amazing to have the full power of the dual processors, the “interesting” new GUI, and USB support all rolled into one system. I remember being quite smitten with Windows from just about then until a couple of years after the release of XP (the fabled “XP SP2” being when I jumped ship and switched to Mac OS X 10.2).
Anyway, yes, Windows 2000 (or “Win 2k” as it was affectionately known in those millennial years) was a true monument, a watershed, a massive accomplishment when compared technically to its immediate predecessor Windows NT 4.0 (SP6a) and an immense effort bring the NT line to “functional parity” with the Windows 9x line. I was stunned that it was replaced so soon by Windows XP (and also, stunned that XP endured for so long thereafter, but that’s another story).