Start a Microsoft Office program (Word, Excel, Outlook, etc.).
Click the File tab in the ribbon.
Select Help in the left column. (Or Account if you are using Office 2013)
Find the section called About Microsoft [Program Name] in the right column. (Select the About [Program Name] icon in Office 2013 or newer)
Review the Version information (e.g., Version: 14.0.6112.5000 (32-Bit) to determine whether you are using a 32- or 64-bit version.
NOTE: You may not necessarily be using a 64-bit version of Microsoft Office even if you are using a 64-bit version of Windows Vista or Windows 7/8.