Help Files opened in Microsoft Word

A Conundrum...

The help files opened from the Help Menu open in Microsoft Word.

Yet the files open correctly in my default HTML app (firefox) when selected from the start menu or directly from the "C:\Program Files (x86)\Mp3tag\help" location.

File Associations are set correctly in Windows 8.1. I have Microsoft Office 2013.

Any suggestions for a remedy?

FIXED: The help files are HTML and are correctly associated with Firefox, however it was the HTM association that Word had grabbed and was the issue.