Microsoft HTML Help projects require binary indexes in certain cases:
•When projects have topic keywords. Topic keywords are saved in the HTML files that reference them.
•When HTML projects are merged. When you merge projects, each CHM file remains in its own project, but keywords from each index file are combined into the master project. Distribute each CHM file along with the master CHM file.
1)Make sure that Microsoft HTML Help is the primary layout.
2)Select Project > File > Project Settings.
3)In the General tab, select Binary Index.
5)Add topic keywords (marked with a key icon ).
6)Merge subprojects if needed.
7)Generate and view the project.
Version-control projects may have more options.