Windows XP is proprietary commercial software. While Microsoft has ended support, the licensing rights remain active. Downloading ISOs from unauthorized sources constitutes copyright infringement in most jurisdictions. Legitimate copies require a valid Product Key specifically for the x64 edition, which are distinct from the common x86 keys printed on the stickers of older PCs.

Since an official version does not exist, any file claiming to be "Windows XP SP3 64-bit" is inherently unauthorized. These files are frequently hosted on unverified third-party sites or peer-to-peer networks. They are prime vectors for malware, trojans, and rootkits. In the context of an older OS like XP, modern malware can easily hide within system files that modern antivirus software on newer machines might not catch when scanning a dormant ISO.