Windows Installer Fix: Error 1718. File was rejected by digital signature policy

I recently was attempting to install a Windows Installer patch on a Windows 2003 server and received the following error:

The patch was rather large (over 600 MB), so after doing some searching I noticed that Microsoft had a hotfix. The hotfix, unfortunately, installed an older version of a file on my system than was currently installed. Because of this, I avoided installing the hotfix.

There was another solution, which was to edit the registry and change a registry key value. Once I changed the registry key value, I restarted the Windows Installer service and the patch was applied successfully.

Windows Installer Patch Error 1718 Fix

To install the patch successfully, I used the following steps:

1. I clicked “Start”, and then clicked “Run”. I type “regedit” in the “Run” dialog and clicked “OK.”
2. Within the registry editor, I navigated to the following key:
   HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Safer\CodeIdentifiers
3. On the right side, I looked for a value called “PolicyScope”. I couldn’t find the value so I created the value as a DWORD.
4. I then set “PolicyScope” to 1.
5. I then closed the registry editor.
6. Next, I clicked “Start”, clicked “Run” and entered “cmd” in the dialog, and clicked the “OK” button.
7. From the command prompt, I stopped the Windows Installer service with the following command:
   net stop msiserver
8. I re-ran the Windows Installer patch package and the patch installed without any issues.

Once the patch was installed, I could easily go back into the registry and reset the “PolicyScope” value to 0 to reset it back to the original value.