Finding an official or safe download for in both 32-bit and 64-bit versions is tricky because Microsoft ended all official support in 2014. Crucially, there is no official 64-bit version of Service Pack 3 . Windows XP Professional x64 Edition is based on the Windows Server 2003 codebase and only ever reached Service Pack 2. Key Version Differences Windows XP 32-bit (SP3) Windows XP 64-bit (SP2) Max RAM ~3.25 GB to 4 GB Up to 128 GB Kernel Original Windows XP Windows Server 2003 Compatibility Best for 16-bit and 32-bit apps Supports 32-bit and 64-bit; no 16-bit Driver Support Widely available Very limited for older hardware Important Review Considerations