Symptoms:
This can often be distinguished by a lack of Word features/toolbars.
Fix:
- Close any open word documents.
- Open a blank word document.
- Select File, Options, General tab and locate the Start up options section (Towards the bottom).
- Untick the Open e-mail attachments... box.
Please note: The above screenshot is taken from Office 365, other version of office may have varying text but will be located in the exact same location.