Note: WinHelp Popups will not work under Microsoft Vista.
Select "Project | HtmlHelp Compiler Options" and click on the "Popups" tab to get to this feature. WinHelp Popups may seem like a strange choice because you are mixing an old technology with a new one, but this is how Microsoft developed their MS Office and Application Development help files. If you choose this option Fast-Help will create a HLP file for you that has the same name as your help file, but with the word "Popups" appended to it. You need to ship this file as well as your CHM file.
Note: You cannot create popup links from one popup to another.
Below is an example of a WinHelp Popup in action:-