Missing Search Tab

I'm working on an HTMLHelp project in RH8 and for the life of me, I cannot get it to display a search tab. I've checked and double-checked that I have the Search tab option selected in the window. When that failed to produce results, I created a new window and, once again, made sure the option was selected, but still no joy. Finally, I created a completely new project with just a couple of topics, and I selected the Search tab option there, but still nothing.

For the record, the option I'm selecting is the Search tab option in the Tri-pane Tabs and Windows section on the Window Properties screen. Am I forgetting something? Doing something wrong?

Can anyone help? I would really appreciate it.

Best wishes.