When you visit Archive.org, consider donating to the organization. Hosting multi-gigabyte ISOs for decades is expensive, and without them, the only copy of Windows XP x64 would be rotting on a forgotten FTP server in a bankrupt OEM's data closet.
To understand the value of the Archive.org copies, you must first understand the context. In 2005, AMD was crushing Intel with the Opteron and Athlon 64 processors. The future was clearly 64-bit, but Microsoft had a problem: The consumer codebase of Windows XP (NT 5.1) was not ready for 64-bit. windows xp professional x64 edition archive.org