Have access denied in opening CHM files?

After installing security update 896358 or Windows Server 2003 SP1, you may find that you cannot view the topics in an HTML help (CHM) file.

The resolution is as follows:

1. Download the CHM file.
2. Right-click on file, and choose Properties.
3. Click Unblock.
4. Open the file.

Further information:

• Read a PDF that explain how to modify registry settings | Download a .reg file to modify the registry automatically
• Read about it on Microsoft Support