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Maybe a Word 2007 question or an Email question, not sure.

When I receive an attached .docx in an email I must save it first and then I can open with Word 2007, the default for that association.

When trying to open the attachment from the email message without saving it first, I get the the notice:

"This file does not have a program associated with it for performing this action. Create an association in the Set Associations control panel".

Other than the "Control Panel / Default Programs / Associate a file type or protocol with a program" I cannot find a "Set Associations control panel".