Microsoft Office 2010 is the first version of Microsoft Office that will ship with both 32-bit (x86) and 64-bit (x64) versions.
If you are currently running a 32-bit version of Windows, you can only use the 32-bit version of Office. However, on a 64-bit Windows platform, you can decide to install either the 32bit or the 64-bit version of Office.
Microsoft recommend installing the 32-bit version of Office, even on a PC running 64-bit Windows, unless you have special needs that require the use of 64-bit Office apps. For example, 64-bit computing is useful when you work with large (over 2GB) Excel or Access files.
If you follow Microsoft’s advice and install the 32-bit version of Office 2010 on your 64-bit Windows Operating System, you can still decide later to swop to the 64-bit version. However, the 32-bit version must be uninstalled before you install the 64-bit version.
Microsoft has published a detailed article which can help you to make an informed choice about Office 2010 and its two versions – 32-bit and 64-bit.
