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Why 32-bit Microsoft apps persist on 64-bit Windows desktops

While Microsoft’s latest server products are 64-bit, Windows desktop apps come in 32- and 64-bit versions. In some cases -- such as Outlook 2010 -- the old 32-bit version wins.

Microsoft moved away from 32-bit systems by making the production versions of its latest server-side products 64-bit only. However, 32-bit applications still reign on 64-bit Windows desktops, including Microsoft Office and Outlook.

Many companies run 64-bit Windows desktops, so one could assume that 64-bit edition of Outlook 2010 is the best choice for them. Interestingly enough, it’s not. Here are some of the reasons you may want to stick with the 32-bit version of Outlook.

Using 64-bit vs. 32-bit applications

What advantages does the 64-bit version of Office -- or any program -- provide end users? It provides access to large amounts of memory, but the only Office 2010 application that benefits from that is Microsoft Excel. The 64-bit version of Office makes it easier to work with unwieldy spreadsheets and pivot tables.

Outlook doesn’t usually work with objects that require gigabytes of memory at a time, so the advantages of going 64-bit aren’t as obvious.

The 64-bit version of Office also introduces a number of cross-compatibility issues. For instance, add-ons that require ActiveX or component object model (COM) controls are a problem and there are quite a few add-ons available for Outlook 2010 and earlier iterations.

Many of these add-ons were not explicitly built for Outlook 2010, but they do work. The problem is that if the controls are configured for 32-bit systems -- and the vast majority of them are -- they will not work with a 64-bit installation of Outlook.

A similar problem exists with another major desktop application -- Adobe Photoshop. There is a long line of third-party add-ons and plug-ins for the 32-bit incarnation of Photoshop. While the 64-bit version is gaining popularity, many long-time Photoshop users resist switching because it means losing most of their 32-bit plug-ins in the process. Even though they know that the 64-bit version is considerably more powerful, a switch means a net loss in functionality.

Many environments also use Visual Basic for Applications (VBA) to script new functionality into Office and Outlook. Fortunately, the introduction of the 64-bit edition of Office doesn’t break compatibility with VBA macros, so you can continue to use them as-is. However, there are key differences in the ways the 32- and 64-bit editions of VBA interact with the system via dynamic link libraries and API calls.

For one, you must explicitly declare if the code you’re using will be compiled according to the older, legacy VBA standard or the newer 64-bit standard. Also, 64-bit Office cannot load any of the MsComCtl Windows common controls, because there is no 64-bit equivalent. For further information, read Microsoft’s documentation on the differences between the 32- and 64-bit versions of VBA.

Finally, when you install Office 2010, you must select either 32-bit or 64-bit. You can’t run them side-by-side on the same machine. You can, however, use a virtual machine (VM) to work around these restrictions. For example, you can install the 64-bit version of Office 2010 on a host machine and the 32-bit edition on a VM running on the same machine.

Remember that all editions of Office and Windows must be properly licensed. Office 2010’s licensing does not allow a single copy to be installed in both a standalone machine and in a VM. However, it can be installed on a PC and a notebook.

As you can see, it doesn’t hurt to use the 32-bit edition of Outlook in almost every situation. The 64-bit edition should only be used where there are a few or no legacy software commitments. That said, be cognizant of possible cross-interactions where other applications expect a 32-bit app.

Serdar Yegulalp
has been writing about computers and IT for more than 15 years for a variety of publications, including,, InformationWeek and Windows magazine.

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