I have a .CHM help file for my application. The problem is on my development machine everything works fine but on other machines, when I access the help file through this code,

hwndHelp = HtmlHelp(hWnd, App.HelpFile, HH_DISPLAY_TOPIC, 0)

it displays the help file but doesnt allow me to navigate to another topic and worst of all it doesnt allow me to close the help file. The application main window remains hidden under the help file. Also on some machines the help window is displayed as maximized and in some as normal.
To exit the help file I have to exit the application.

Could anybody throw some light?
Thanks.