The key difference between 32-bit and 64-bit Windows XP-based computing lies in the 64-bit versions ability to use much more system memory. Windows XP Professional x64 Edition initially supports up to 128 gigabytes (GB) of RAM and up to 16 terabytes of virtual memory. Physical memory support will grow in the future as hardware capabilities expand. Data in memory is accessed thousands of times faster than it is on a disk drive, offering a tremendous performance benefit for applications that are developed to use this greater system memory. Built on the Windows Server 2003 SP1 code-base, Windows XP Professional x64 provides increased reliability for business critical desktop computing.Users can now experience the stability and security of a server product on their PC. With Windows XP Professional x64 Edition, users can confidently run their most mission critical applications with increased reliability, security, and performance. The image showing four available is merely yo confirm stock availability at time of listing. Buyers will receive one sealed piece of software. Guaranteed to install / activate / register on your computer. The software is a full installation with certificate of authenticity with this genuine software. There is no requirement to have a previous version installed on your intended computer. Genuine & Legal OEM Version only. Thank you for viewing this listing. The item "Microsoft Windows XP Pro x64 Edition SP2C for System Builders 1pk (ZAT-00124)" is in sale since Friday, April 24, 2020. This item is in the category "Computers/Tablets & Networking\Software\Operating Systems". The seller is "sandy-polar-honey" and is located in Clynder, Argyll and Bute. This item can be shipped worldwide.