A. Office 2010 is the first version to ship with 32-bit and a 64-bit versions and many organizations are wondering which to use.
About 50 percent of Windows 7 deployments are 64-bit, particularly machines that have 4GB or more of RAM. While it may seem obvious to just install the 64-bit version of Office 2010 if you have the 64-bit version of Windows 7, this may not be the best approach.
Many organizations use various controls, add-ins, and Visual Basic for Applications code that are 32-bit. 64-bit Office can't load these 32-bit binaries, so unless you've done a full analysis of the add-ins, controls, and so on that you use with Office and determined 64-bit versions are available, you should use the 32-bit version of Office 2010.
There are advantages with using the 64-bit version of Office 2010, particularly if you use very large Excel spreadsheets (over 2GB in size) or very complex project files. However, if there's not a specific need to go 64-bit Office, you should use the 32-bit version to ensure compatibility by default, even if you install Office 2010 on a 64-bit OS.