While it looked exactly like the classic XP we all know, its "under the hood" components were significantly different. It was actually based on the , which made it famously stable but notoriously picky with drivers.
Windows XP Professional x64 Edition is a fascinating bridge between classic XP and modern 64-bit computing. Preserved on archive.org, it offers immense RAM support and the NT 5.2 kernel’s stability, but demands pure 64-bit drivers and sacrifices 16-bit app compatibility. Best experienced in a VM or on period-correct hardware (2005–2009). windows xp professional x64 edition archive.org