See http://support.microsoft.com/?kbid=319956 "The Answer Wizard and the
Help Index tabs appear blank when you use Help in an Office program".

Jim H. wrote:
When I click on the Help menu, the Help search window appears and I can
search for and see help topics. But, when I double-click on a topic, nothing
happens, no window pops up with help information.

What's up?

Excel 2000 / Windows XP SP2