>I am using HTML Help Workshop for creating Help file.
>I attached it to my application. It works. Appreciate you help.
>What I don't understand where I can create topic index.
> hwndHelp = HtmlHelp(hWnd, HelpFileName, HH_DISPLAY_TOPIC, 0)
>Where HH_DISPLAY_TOPIC can be defined?
>And what is CHI file?
>
>Thanks.

Topics can be defined in the help project. I don't know what a CHI file is, but a CHM file is the final result of creating a help project and compiling it. This file is what the application will open to access the program's documentation. See http://msdn.microsoft.com/library/default.asp?url=/library/en-us/htmlhelp/html/vsconoverauth.asp