Documents created with Microsoft Office 2007 or newer are saved as ZIP in Internet Explorer 9

SYMPTOMS

CONDITIONS:

• Internet Explorer 9 or 10 is used.
• Documents created with Microsoft Office 2007 or newer are saved with old type extension. i.e. 'DOC' instead of 'DOCX'.

CAUSE

Internet Explorer by default protects the users with a function referred as MIME Handling. Office 2007+ files actually have ZIP archives signatures (i.e. 06 20 08 20 20 20). The Microsoft Internet Information Services (IIS) MIME Type configuration, combined with the fact that Office 2007+ documents were saved with an improper extension, is the cause of this behavior.

RESOLUTION

Make sure that the Office 2007+ documents are saved with the appropriate file extension, i.e. 'DOCX' rather than 'DOC'.

Alternatively, it's also possible to change Microsoft Internet Information Services (IIS) MIME Types configuration so that the Web Clients provide the right MIME types to Internet Explorer when downloading. But please note that this may introduce a misbehavior when the Office documents are genuinely of 97-2003 type (i.e. proper 'DOC' files). 

• Open the IIS Microsoft Management Console (inemgr).
• Navigate to the Default Web Site, where all ZyLAB Web Clients are stored under.
• In the middle pane double-click MIME Types.
• Sort by extension and find the necessary exception, i.e. 'DOC'.
• Make sure the MIME type associated with it is correct.

http://blogs.msdn.com/b/vsofficedeveloper/archive/2008/05/08/office-2007-open-xml-mime-types.aspx

NOTE: For security reasons, it is not recommended to disable the MIME Handling feature in Internet Explorer. If you disable this feature, users can download malicious content, disguised with an incorrect filename extension. Once a file is downloaded, an incorrect extension handler can run the file, enabling the malicious content to cause damage. Refer to the Microsoft article below.
http://technet.microsoft.com/en-us/library/cc749557

APPLIES TO

6.3; 6.4; 6.4 Service Pack 1