When the system requirements for Microsoft Office 2010 were first posted, we noticed that Windows XP 64-bit was mysteriously absent. We contacted Microsoft, and the company explained that while deciding on which versions of Windows to support in the next release of Office, it weighed the user experience behind the versions against broadly dropping support.
"For the Microsoft Office 2010 release, we will not support Windows XP 64-bit," a Microsoft spokesperson confirmed with Ars. Upon further inspection, we also noticed Windows Server 2003 support was missing. "For the best productivity and user experience, the benefits of 64-bit computing with Office 2010 is best experienced by utilizing the newly introduced 64-bit version of Office 2010 with Windows 7 (64-bit) or Windows Vista (64-bit) version." In short, Microsoft does not think the experience will be good enough on its previous operating systems.