ARS Technica reports Office 2010 will only support the 32-bit version of Windows XP, and that support for Windows Server 2003 has been dropped as well. A Microsoft spokesperson said that while deciding which versions of Windows to support in Office 2010, the developers weighed the user experience behind the versions against broadly dropping support. Probably the software giant would want to kill the 32-bit version for Windows XP as well, but this would cost them a lot as the 32-bit version of Windows XP is still world's most widely used operating system.
"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."
Here's the full list of operating systems supported by Office 2010:
Office 2010: Windows XP (32-bit only), Windows Server 2003 R2 with MSXML 6.0 installed, Windows Vista SP1+, Windows Server 2008 SP2+, Windows 7, and Windows Server 2008 R2. Except for XP, 32-bit and 64-bit versions of Windows are supported. Terminal Server and Windows on Windows (WOW) (which allows installing 32-bit versions of Office 2010 on 64-bit operating systems) are also supported. Naturally, running a 64-bit version of Office 2010 is not possible on a 32-bit version of Windows.