You are upgrading 32-bit Microsoft Office 2013 on 64-bit Windows.If you choose to, you may install 64-bit Office 2013 instead. ...

You are upgrading 32-bit Microsoft Office 2013 on 64-bit Windows.If you choose to, you may install 64-bit Office 2013 instead. Installing 64-bit Office 2013 may introduce compatibility issues with other 32-bit software on your system.Click the Help button for more information on choosing an installation platform and instructions on installing 64-bit Office 2013.Otherwise, click "Upgrade" to continue with 32-bit Office 2013 installation.