You can remove any window from your project including custom/secondary windows and the main window used as the default window for your project. If you remove the default window, your project settings will not be configured to display the Help system in a custom window.
When you view the compiled .CHM file in the HTML Help viewer, your Help system will be displayed using the viewer's default settings.
Click the Project tab.
Open the Windows folder.
Right-click the name of the window to remove and select Delete.
At the prompt, click Yes to confirm that you want to remove the window.
Compile your Help system for the changes to take effect.