Which Windows version was the first 64-bit edition?

The first 64-bit edition of Windows in this quiz’s client-release context was Windows XP 64-Bit Edition. Microsoft released it for systems using Intel’s Itanium processor, making it distinct from the later Windows XP Professional x64 Edition for ordinary x86-64 PCs.

Windows XP 64-Bit Edition first appeared in 2001 for IA-64 Itanium systems. A revised 2003 edition followed, based on the Windows Server 2003 code base. These editions were aimed at specialized workstations and servers rather than typical home computers, and they had limited compatibility with older software.

Microsoft later released Windows XP Professional x64 Edition on April 25, 2005. That version supported the x86-64 extensions used by AMD64 processors and Intel 64 chips, which became the dominant form of 64-bit personal computing. It could run many 32-bit programs through Windows-on-Windows 64, or WoW64.

The phrase “first 64-bit edition” can be confusing because Microsoft had experimented with 64-bit hardware support in earlier Windows NT ports and server products. In the familiar Windows client lineup represented by the answer choices, Windows XP is the accepted answer.