Windows Help requires an application to explicitly cancel Help so that it can free any resources it used to keep track of the application and its help files. The application can do this at any time by calling the WinHelp function and specifying the HELP_QUIT command. Note that this is not true for the pop-up instance of Windows Help. An application should not try to close the pop-up instance.
If an application has made any calls to WinHelp, it must cancel Help before it closes its main window (for example, in response to the WM_DESTROY message in the main window procedure). An application needs to call WinHelp only once to cancel Help, no matter how many help files it has opened. Windows Help remains running until all applications or dynamic-link libraries (DLLs) that have called WinHelp have canceled Help.
To close the training card instance of Windows Help, you must specify both the HELP_TCARD and HELP_QUIT commands when calling the WinHelp function. An application does not need to cancel the training card instance of Windows Help if the user cancels it first. Windows Help notifies an application when the user cancels the training card instance by sending the WM_TCARD message with the wParam parameter set to IDCLOSE.