By default Office 2010 will open documents in protected mode that fail validation, have been downloaded from the internet, are located in potentially unsafe location and include attachments. Protected view opens the document in read-only mode thus minimizing the exposure to some potential security threat.for any reason, you do not like such a feature, here is a simple tutorial to disable it in a couple of steps.
1. Open Word or Excel in Office 2010.
2. Click the Office button. Go to File Menu, Office Backstage, and click Options.
3. In the left pane, Click Trust Center.
4. Now, on the right pane, click the Trust Center Settings button.
5. At this point you should be in the Trust Center dialog window.
6. In the left pane, click Protected View.
7. Untick the following options:
Enable Protected View for files that fail validation
Enable Protected View for files originating from the Internet
Enable Protected View for files located in potentially unsafe locations
Enable Protected View for Outlook attachments
8. Click OK