Office 2010 – 32-bit or 64-bit?

Office 2010 is the first version of Microsoft Office to be available in 32-bit and 64-bit versions.

If you are running a 64-bit version of Windows, you should install 64-bit Office, right?

WRONG!

Official advice from Microsoft is to use the 32-bit version unless you specifically need to make use of some of the capabilities only available in the x64 version such as Excel 2010’s support for larger data sets.

The problem is that Office 2010 x64 introduces breaking changes that mean 32-bit add-ins may not work in 64-bit Office. For a complete discussion see
http://msdn.microsoft.com/en-us/library/ee691831(office.14).aspx

Office 2010 System Requirements

Minimum CPU and  RAM requirements are unchanged from Office 2007, but the footprint of most Office applications have gotten larger. Most standalone application disk-space requirements have gone up by 0.5 GB and the suites have increased by 1.0 or 1.5 GB.

So, in short, if your PC can run Office 2007, it will be able to run Office 2010. If you just acquired a brand new PC, it also will be able to run the forthcoming suite. But if you’re using Office 2003, there are no guarantees you’ll automatically be able to run Office 2010 on the same hardware.

The 32-bit version of Office 2010 will run on the following 32-bit operating systems: XP with Service Pack (SP)3, Vista SP1, Windows 7, Windows Server 2008 and Windows Server 2003 R2 (with MS XML). The 64-bit version will run on on 64-bit versions of all of these same operating systems, with the exception of Windows Server 2003 R2.

via Mary Jo Foley