Microsoft continued to use 2000 on Alpha to work out bugs in 64bit support since it was the only 64bit platform they had supported that had operational hardware (support for PPC was only for 32bit), making it important bit in support of Itanium and soon later amd64 ports.
Some of the details made for Alpha support (including extended support for software like FX!32) are now backbone of x86-on-ARM support in windows ARM builds
We also had a bunch of 1000 and 1000a's, and an AlphaStation running AltaVista firewall all on NT.
An ALR 6x6 (6* Pentium Pros) was faster for Windows than the fully loaded out AS4100 IIRC. Except that the 4100 supported more memory and PCI slots IIRC.
I worked at a mostly DEC shop for a while. They had transitioned their main product from VAX to Alpha. Most of the systems ran Digital Unix and VMS, but there was an AlphaServer with NT 4.