I recall using XP x64 edition on an Athlon64. I remember it having such poor software support that it was barely usable. I heard it was actually a version of Windows Server that they put the XP GUI on top of, but I'm not sure if that's true (Wikipedia only seems to partially corroborate it).
>I heard it was actually a version of Windows Server that they put the XP GUI on top of
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.
I ran Windows XP x64 on my personal desktop until 2013. It was solid and dependable for me, though I did heavily customise it (custom Visual Styles themes, disabling features I didn’t like, some hacks to bring-forward sone features from Windows 7, etc)
Windows Server and Client were always much closer than appeared at first glance, as long as you lined up the versions. So it almost certainly was as described.
