Advantages of Running Office 2010 64-bit 

  • Ability to utilize additional memory.
  • Excel 2010 can load much larger workbooks. Excel 2010 made updates to use 64-bit memory addressing to break out of the 2-GB addressable memory boundary that limits 32-bit applications.
  • Microsoft Project 2010 provides improved capacity, especially when you are dealing with many subprojects to a large project.
  • Enhanced default security protections through Hardware Data Execution Prevention (DEP)

Disadvantages of Running Office 2010 64-bit 

  • Might affect compatibility of COM Add-ins and ActiveX controls

Add-in (COM) DLLs (dynamic link libraries) and ActiveX controls that were written for 32-bit Office will not
work in a 64-bit process. As a result, Office 2010 64-bit solutions that try to load 32-bit ActiveX controls or
DLLs will not work. 64-bit Office 2010 installations will only run 64-bit controls. Computers can have 64-bit
and 32-bit controls installed and Microsoft Office 2010 64-bit can only run the 64-bit versions of the controls.
The workaround for resolving these issues is to obtain 64-bit compatible controls and add-ins or to install
Office 2010 32-bit (WOW).
In addition to controls that load into Office applications, there are also Web-based solutions that use ActiveX
controls in Microsoft Internet Explorer. Office 2010 64-bit editions install some Office 32-bit client-side
controls for supporting solutions in a 32-bit browser (the default browser on current 64-bit Windows
systems). The Edit in Datasheet View functionality is not supported if you install Office 2010 64-bit clients.
The Datasheet View functionality is available if you install Office 2010 32-bit.

  • Might affect compatibility of Microsoft Access MDE/ADE/ACCDE files

Databases that have had their source code removed (such as .mde, .ade, and .accde files) cannot be
moved between 32-bit and 64-bit editions of Office 2010. Such databases that are created by using 32-bit
Office (any version) can be used only with 32-bit Office, and a database that is created on 64-bit Office can
be used only on 64-bit Office.

  • In-place activation

The following issues might occur if there is not a match between the bitness of Office 2010 and registered
· An OLE server may not instantiate in place and may fail to open if the application registered is not the
same bitness as the version of Office installed. For example, if your OLE Server application is 32-bit and
the version of Office installed is 64-bit.
· Inserting an object into an Office 2010 application document may fail in cross-bitness scenarios. For
example if you insert a 32-bit object in a 64-bit Office 2010 application document.

  • Graphics rendering

There are differences between the 32-bit and 64-bit Graphics Device Interface (GDI) that might have
performance implications because of the lack of MMX support on 64-bit. Intel’s MMX technology is an
extension of the Intel architecture (IA) instruction set. The technology uses a single-instruction, multiple-data
(SIMD) technique to speed up multimedia and communications software by processing data elements in

  • Macros with Visual Basic for Applications (VBA)

VBA code that uses the Declare statement to access the Windows application programming interface (API)
or other DLL entry points will see differences between 32-bit and 64-bit versions. The Declare statement
must be updated with the PtrSafe attribute after inputs and outputs to the API have been reviewed and
updated. Declare statements will not work in 64-bit VBA without the PtrSafe attribute. New data types are
added to 64-bit Office 2010 VBA: LongLong and LongPtr.


Summary Installation recommendations

If users in your organization depend on existing extensions to Office, such as ActiveX controls, third-party add-ins, in-house solutions built on previous versions of Office, or 32-bit versions of programs that interface directly with Office, we recommend that you install 32-bit Office 2010 (the default installation) on computers that are running both 32-bit and 64-bit supported Windows operating systems.

If some users in your organization are Excel expert users who work with Excel spreadsheets that are larger than 2 gigabytes (GB), they can install the 64-bit edition of Office 2010. In addition, if you have in-house solution developers, we recommend that those developers have access to the 64-bit edition of Office 2010 so that they can test and update your in-house solutions on the 64-bit edition of Office 2010.