As a side-note, it's interesting that all of the released versions of NT on Alpha were 32 bit.
Raymond Chen has a blog post[0] about using Alpha to develop 64bit Windows before Itanium hardware was available.
Virtually Fun has some more excellent background on finding a compiler for 64bit Windows[1], finding a copy of Windows 2000 64bit for Alpha AXP[2], and a detailed article about making an ISO from the found copy.
[0] https://learn.microsoft.com/en-us/previous-versions/technet-...
[1] https://virtuallyfun.com/2023/05/05/hiding-in-plain-sight-th...
[2] https://virtuallyfun.com/2023/05/15/windows-2000-64-bit-for-...
[3] https://virtuallyfun.com/2023/06/26/axp64-2210-installation-...
Yes, the released, as well as final RC for 2000, were still 32bit mode.
There's a quote, possibly from Raymond Chen, about how they originally naively thought they will be able to just change size of an int, IIRC, and that backfired seriously.
That said, 64bit release of windows was supposed to happen on Alpha had Compaq not pulled the plug