Andre has described the process for retail CD/DVD. If you bought online download, you will have to return to the site you bought it from, log in with your email address and find the 64 bit download link. It probably won't be obvious, but it will be there
To get the full installer for Office 2010, logon to the
Account Management Console, click the Download button next to your trial order and then instead of clicking the “Install Now” button, click on the “Advanced Options” link underneath. At the top of the Advanced Options pop-up that you’ll get, you can select
between the 32-bit, the 64-bit or the Click-to-Run installer.
The next question is, why do you want 64 bit Office. MS still recommends 32 bit. The main reason for 64 bit is if you are dealing with Excel files larger than 2GB.
Office 2010 is the first release of Office that contains 64 bit edition. It’s recommended to install the 32 bit version Office 2010 due to compatibility issues however if you still want to try 64 bit version keep these in mind.
·32 bit version works on both 32 bit and 64 bit windows operation systems. But 64 bit version Office 2010 must be installed on 64 bit windows operation systems.
You can’t upgrade from 32 bit Office 2007 to 64 bit Office 2010 directly, you have to uninstall existing 32 bit Office products prior to install 64 bit Office 2010. (It’s okay to upgrade Office 2007 to 32 bit Office 2010 on either 32 bit or 64 bit operation
You can’t run 64bit and 32bit office products side by side. For example, you can’t have side by side installation of 32 bit OneNote 2010 and 64 bit Outlook 2010
Some of 32bit Office Add-Ins might not work on 64 bit Office 2010.
64-bit Office 2010 product backup is available at
http://www.office.com/backup. However, we recommend most users install the 32-bit version of Office 2010. The 64-bit installation of Microsoft Office 2010 products are for users who commonly use very large documents or data sets and need
Office 2010 programs to access greater than 2GB of memory. There are some technical limitations with the 64-bit version.
The recommendations for which edition of Office 2010 to install are as follows:
·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.
Side-by-side installations No support is provided for side-by-side installations of 64-bit and 32-bit editions of Office, including across applications. For example, there is no support for side-by-side installations
of the 2007 Microsoft Office system 32-bit with Office 2010 64-bit, or for Microsoft SharePoint Workspace 2010 64-bit and Microsoft Excel 2010 32-bit.