There were pre-release 64 bit alpha versions of win2k, but otherwise you needed XP/2k3 for 64 bit. XP for amd64 was a bit of a shitshow with drivers (especially on consumer-grade computers), though. It wasn’t until vista that it ironically got better on that front, though people held out upgrading because of how terrible it was…
yeah while 2K was their best ever single breakthrough improvement, it was a v1 and XP/2003 in classic mode was a more refined 2K eg more drivers and better plug and play, more graphics compatibility. And 2003 Active Directory had a number of quality of life improvements.
Windows 7 with classic UI is probably the most-recent decent version.