Выдержка из MSDN

The HTML Help API has one function that displays a help window. Using the API commands, you can specify which topic to display in the help window, whether the help window is a three-pane Help Viewer or a pop-up window, and whether the HTML topic file should be accessed via a context ID, an HTML Help URL, or a Keyword link (KLink) lookup.
HTML Help API syntax
HWND HtmlHelp(
HWND hwndCaller,
LPCSTR pszFile,
UINT uCommand,
DWORD dwData) ;
Parameters
hwndCaller
Specifies the handle (hwnd) of the window calling HtmlHelp(). The help window is owned by this window.
When the help window is closed, HtmlHelp() will return focus to the owner unless the owner is the desktop. If hwndCaller is the desktop, then the operating system determines where focus is returned.
In addition, if HtmlHelp() sends any notification messages from the help window, they are sent to hwndCaller as long as you have enabled notification message tracking in the help window definition.
pszFile
Depending on the uCommand value, specifies the file path to either a compiled help (.chm) file, or a topic file within a specified help file.
A window type name can also be specified, preceded with a greater-than (>) character.
If the specified command does not require a file, this value may be NULL.
uCommand
Specifies the command to complete.
dwData
Specifies any data that may be required, based on the value of the uCommand parameter.
Return Value
Depending on the specified uCommand and the result, HtmlHelp() returns one or both of the following:
The handle (hwnd) of the help window.
NULL. In some cases, NULL indicates failure; in other cases, NULL indicates that the help window has not yet been created.
Example
The following example calls the HH_DISPLAY_TOPIC command to open the help file named Help.chm and display its default topic in the help window named Mainwin. Generally, the help window specified in this command is a standard HTML Help Viewer.
HWND hwnd =
HtmlHelp(
GetDesktopWindow(),
"c:\\Help.chm::/Intro.htm>Mainwin",
HH_DISPLAY_TOPIC,
NULL) ;

2 Вентик

Если есть готовый пример, то посмотри откуда он берет файлы помощи. Для этого открываешь системное меню, там Jump yo URL, и Current URL.

Если спрятать файл р ресурсы, то это не поможет от декомпиляции.

Сам HTML Help ложит свою помощь по адресу mk:@MSITStore:С:\WINDOWS\help\htmlhelp.chm::/1hh.htm