Generally, MS recommends running Office as a 32-bit application, even on 64-bit systems. That's largely because various 3rd-party addins aren't compatible with 64-bit Office.

You might need to uninstall both Office 2010 and Outlook 2007, then reinstall Outlook 2007 followed by Office 2010. When reinstalling Office 2010, you might also need to do a custom install so as to preserve the Outlook 2007 installation.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]