In the Dex - Identifying the build number of a Development Dictionary post, we covered using the Windows Explorer to get the dictionary version from the file properties.  This only works if the .DIC extension is correctly associated with Dexterity as a Dexterity Dictionary.

On my system, I find that every time Windows Update installs updates to Microsoft Office, the .DIC extension is changed to be associated with Notepad as a Text Document.

Below are the steps to change the association back using the Registry Editor.

1. Click Start >> Run..., type "RegEdit" and press Enter or if Run is not enabled, Click Start and in the Search field, type "RegEdit" and press Enter.
    
2. Locate the Computer\HKEY_CLASSES_ROOT\.dic node.
    
3. Change the string value for the Default registry key from txtfile to DIC_auto_file.
    
4. Close the Registry Editor window.

DISCLAIMER:  The Registry Editor should be used carefully and only if you are comfortable making registry changes.  Use of the Registry Editor is not supported.

Attached to the bottom of this post is a zipped .reg file which can be double clicked on to make the same change to the registry.

Hope this helps. 

David