If your Search tab is completely empty in your HtmlHelp file it is because Full text search has not been fully enabled. Select "Project | HtmlHelp Compiler Options" and check the box "Full Text Search Information".
It could also be that one of the required dlls is not registered. Please open an MS-Dos prompt and go to the "c:\winnt\system32" directory in NT or Win2000 or XP System, your "c:\windows\system" directory in Win95/98. Type in:-
You should receive either a confirmation message that it has been registered successfully or that it is already registered. Then recompile your CHM project, no need to reload Fast-Help. Do you now get search results when you type in a word and press Enter?