.HHK File

The hhk file extension is related to the Microsoft Help, a service included in Microsoft Windows, which allows developers to create help documents for its programs.

Index of files accessible by Microsoft HTML Help, a Web-based help interface.

A hhk file extension is associated with the Microsoft Help and used for its HTML help index files.

How to open:

Probably not meant to be accessed by the user.

How to convert:

There is probably no real way how you can convert this particular file type to anything else.