Have you tried repairing the Office installation (via Programs & Features > Microsoft Office > Change in the Windows Control Panel)?

It's also possible the inability to open .doc attachments without first saving them is a function of your email app's security settings. Windows Live Mail, for example, has a setting that prevents the opening of attachments that could contain viruses. Word .doc files fall into this category, but .docx files do not.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]