When you save a document in the encrypted binary file format in a 2007 or 2010 Microsoft Office application, you receive the following message:
"This document is both encrypted and password protected. The Office Open XML Formats available in the 2007 release provide stronger encryption. Do you want to increase the security of this document by converting to an Office Open XML Format?"
If you click Yes on this message, you receive the message the next time that you save a document in the encrypted binary file format. Additionally, if you press CTRL+SHIFT+I, Alert ID 701726 is displayed in the lower-right corner of the message dialog box.
You apply the 2007 Microsoft Office suite Service Pack 2 (SP2) or you have Microsoft Office 2010 installed. If you click No on the message that is mentioned in the "Symptoms" section, you no longer receive the message when you save a document in the encrypted binary file format. This sets the value of the NoPromptForRC4Encryption registry key to 1. In earlier versions of the 2007 Office suite SP2, you had to set the value manually. The registry key is located under the following registry subkey:
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
To bring the prompt back, you can change the value of the NoPromptForRC4Encryption registry key to 0 or delete the registry key. To do this, follow these steps:
Microsoft Office 2007:
Click Start, click Run, type regedit in the Open box, and then click OK.
Locate and then click the following registry subkey: