Are you planning to upgrade from Office 2007 to the 64-bit (x64) version of Office 2010? Take note that you will have to completely uninstall all of your current Office 2007 applications, including Word, Outlook, PowerPoint, Excel, Access, OneNote, InfoPath, Project, SharePoint Designer, Groove, Visio, and Publisher.
“Why should I care,” you ask? The main reason is that many common Office add-ins and application that interact with Office will not work with the 64-bit version of Office. You may find yourself unable to use an add-in or application on which you rely heavily. For example, if you rely on an add-in for Word to be able to save and load documents to your organization’s document management system, you might be out of luck until the vendor creates a 64-bit version of the add-in.