When a CHM help file is placed on a networked or mapped drive, or downloaded directly from the Internet, only the table of contents is shown and it is impossible to navigate to any topic: their content is empty. This is a restriction due to a Microsoft security patch as detailed in this Microsoft support page. The only solutions to avoid this problem are:

  • Copy the CHM help file to a local drive
  • Apply the registry patch detailed in Microsoft's support page to each computer accessing this CHM help file

Other possible solutions are to make sure your help file isn't in a path with symbols such as "#" (sharp). Once again, try to copy it locally before launching it.

And in some cases, you can have access to an "unblock" button in the properties page of the help file:

  • Right click on the file in Windows Explorer then go to its properties
  • Click the "unblock" button. This button is not available in all systems though