Select "Project | HtmlHelp Compiler Options" and click on the "Popups" tab to see this option. HtmlHelp natively supports only one kind of Popup, plain text popups. But "Plain Text Popups" do not support images, links or any formatting at all. They are very limited, so Fast-Help has extended this with two further options, Html Active X Popups and WinHelp Popups. Each has their pros and cons but one of them will suit your needs, so you can choose which is best for you.
You can switch between any of these options at any time. Click below to see more on each option:-