In a way, yes. It used the kernel from Server 2003.[1] Server/client kernels were unified for Vista SP1 and Server 2008, and not sooner just because the 2008 release lagged behind Vista's debut.
Prior to Vista, this kernel difference meant drivers for Windows server and client often had to be different builds. An anecdote that I recall was that although xp64 and 2003x64 could share drivers, it was typical to see drivers "not provided" for xp64, so the people who wanted that kernel just ran Windows Server as a desktop OS instead.
1: https://en.wikipedia.org/wiki/Windows_XP_Professional_x64_Ed...
So, you could get a 64-bit computer running Windows, but you wouldn’t be able to play Pinball, or read your emails, or run some other software you needed to work.
Oddly enough, the situation was much better with 64-bit Unix, where your usual tools worked flawlessly.
Also, that’s why we all should write unit tests.
It was but not when you think... 64-bit NT was never released. NT on Alpha was 32-bit.
It only leaked this month. I wrote about it:
I don’t think one could run Outlook on them.