Tip: For Windows 64 OS, microsoft ship both a 32 bit and 64 bit version of HTML Help runtime. So when modifying registry settings
remember to change both (a 32 bit app may spawn the 32 bit version while opening a .chm from explorer may open the 64 version).
The 32 bit registry area is under HKEY_CURRENT_USER\Software\Wow6432Node\
Here are the main HH security updates. The KB articles below contain work-a-rounds to get around the security restrictions. Use with caution.
The right hand pane of the help viewer shows the IE message "Item canceled" or "Page cannot be displayed".
Note: Microsoft should display a clear message telling the confused user why content is not showing in the help file.
Try emptying your Temporary Files Cache (Control Panel > Internet Options > General page > Delete Files...). When the cache fills up IE cannot render its content correctly.
Note: Microsoft should fix this bug. Is IE7 ok?
Shortcuts can be disabled on the local PC by setting the following policy. See KB810687, KB323180
Registry Key: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System\
To enable shortcuts simply deleted the registry key name "HelpQualifiedRootDir". Even HelpQualifiedRootDir=<empty string> will enable the policy. If the problem persists and the registry key name reappears then check with your network administrator as they are probably enforcing the policy.
Note: Microsoft should display a clear message "shortcuts disabled via policy. See your network administrator". Displaying an unrelated script error is clearly misleading and wastes everyone's time.
Certain Help related DLLs can become unregistered. Usually due to a faulty installer or a 3rd party help authoring tool vendors trying to cut corners. Some vendors (usually Chinese based) actually install and register individual Microsoft help DLLs (they should use hhupd.exe and HtmlHelp.exe). These DLLs are often installed to the wrong location and eventually DLL mismatch problems occurs.
Download and run MJsDiags (above). This will check and repair DLL problems.
See also: HH FAQ