To add a secondary window
Open a project (.hhp) file, and then click Add/Modify Window Definitions.
Adds or edits window definitions and the general appearance of the HTML Help Viewer. Type a name of up to eight characters for the secondary window you are adding.
Click the General, Buttons, Position, Files, Navigation Pane, Styles, and Extended Styles tabs to create the features you want for your secondary window.
Note
You can also create a window without a Navigation pane.