32-bit and 64-bit versions of Windows seem to throw a lot of people for loops. 64-bit versions of software can only be installed on 64-bit versions of Windows but 32-bit software can be installed on both 32-bit and 64-bit Windows (thanks to the WoW64 extensions that have really improved the experience since Windows XP 64).
The “bit-ness” of Windows is actually summarizing a mathematical problem that is addressed by 64-bit Windows. 32 bits means Windows can address about 3.2 gigabytes of RAM (summarized as 4GB). If you have more RAM than 3.2GB and a 32-bit version of Windows installed, that extra RAM is being wasted. A bit is a binary placeholder and 32 bits means the field is 32 spaces long, like the ones place, tens place, hundreds place, and so on. 64-bit Windows gives the operating system much more RAM to work with (the OS actually controls the bottleneck more than the math now).
Microsoft Office is a popular application and when given the option to download, for example with Office 365, you are given the option of downloading the 32-bit installer or the 64-bit installer since Office 2010. Many people will look to see if their Windows is 32-bit or 64-bit and choose the matching version. While that is fine for most applications, Office is a rather complex product and Microsoft recommends the 32-bit version of Office in most cases.
They have softened the language a bit in recent years but the reasoning still stands. To reduce compatibility issues in the future, it is recommended to use the 32-bit version of Microsoft Office. Unless you are working with large and complex Excel spreadsheets or Access databases or PowerPoint presentations with lots of multimedia, Microsoft Office will be just fine within the confines of the 32-bit version.
From TechNet:
32-bit Office is recommended for most users
We recommend the 32-bit version of Office for most users, because it’s more compatible with most other applications, especially third-party add-ins. This is why the 32-bit version of Office 2013 is installed by default, even on 64-bit Windows operating systems. On these systems, the 32-bit Office client is supported as a Windows-32-on-Windows-64 (WOW64) installation. WOW64 is the x86 emulator that enables 32-bit Windows-based applications to run seamlessly on 64-bit Windows systems. This lets users continue to use existing Microsoft ActiveX Controls and COM add-ins with 32-bit Office.
If you uses third party add-ins, you may only be able to use the 32-bit Office and switching from 64-bit Office will require an uninstall and reinstall.
TechNet lists these reasons to use the 64-bit Office:
- Excel experts with complex worksheets
- Project files over 2GB
- In-house Office solution developers for testing
- Security enhancement by default with hardware DEP (Data Execution Prevention).
From my experience, that means most people are able to use the 32-bit version of Office and if you are able to use the 32-bit Office enterprise-wide, your developers do not need to test 64-bit Office cases. Keeping the same solution across the enterprise makes deployment and updating simpler and more efficient.