CHM Files in Windows 7

The release of Microsoft Security Update 896358 prevented Windows 7 users from being able to open CHM Help files that are stored in network locations. To allow CHM files stored in network locations to be accessed from Windows 7 machines on the network the following registry change has to be made.

  1. Click Start, click Run, type regedit, and then click OK.
  2. Locate and then click the following subkey:
    If this registry subkey does not exist, create it.
  3. Right-click the ItssRestrictions subkey, point to New, and then click DWORD Value.
  4. Type MaxAllowedZone, and then press Enter.
  5. Right-click the MaxAllowedZone value, and then click Modify.
  6. In the Value data box, type 1, and then click OK.
  7. Quit Registry Editor.

Setting the value to 1 in step 6 specifies that the Local Intranet zone is to be trusted.  This value can be adjusted based on where the .chm files reside based off of the Internet Explorer site zone assignment list below.

Intranet Zone: 1
Trusted Sites Zone: 2
Internet Zone: 3
Restricted Sites Zone: 4

At this point the CHM files that are stored in the network location should function as expected on the Windows 7 workstation.