Fun fact: Windows XP x64 edition was based on Windows Server 2003, so under AD management (I think that's where this would appear), any XP x64 machines would show up as Server 2003 machines.The first 64bit version (for Itanium 1 only) was NT 5.1 too. 64bit 2003 (for Itanium 2) and x64 were 5.2.
That totally didn't throw sysadmins for a loop