System Error 126 when you start the Windows Modules Installer service (TrustedInstaller): The specific module could not be found

This article helps fix the System Error 126 that occurs when you start the Windows Modules Installer service.

Applies to:   Windows 7 Service Pack 1, Windows Server 2008 R2 Service Pack 1
Original KB number:   959077

Symptoms

When you start the Windows Modules Installer service, you receive the following error message:

Screenshot of the Windows Modules Installer service Error 126.

You also receive an error message at the command prompt:

Screenshot of the error message at the command prompt: System error 126 has occurred.

Cause

This issue occurs if the following registry subkey is changed:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\Version

Resolution

To resolve this issue, you have to re-create the expandable string value of the registry subkey that is mentioned in the Cause section.

First, you have to check whether the registry subkey exists. To do this, start Registry Editor, and then browse to the subkey that is mentioned in the Cause section. If the subkey does not exist, you must create it. To do this, follow these steps:

  1. Locate the C:\Windows\Servicing\Version directory, and note the name of the subfolder in this directory. It will be named something like 6.1.7600.16385. This is your TrustedInstaller ID.

  2. Copy the subfolder name to the clipboard, and then paste it into Notepad for safekeeping.

    Screenshot of the subfolder name in this directory.

    Note

    In this example, the TrustedInstaller ID is 6.1.7601.17592.

  3. In the C:\Windows\WinSxS directory, find a subfolder whose name begins with one of the following strings. (In the following subfolder names, the placeholder TrustedInstaller ID represents your TrustedInstaller ID.)

    For 32-bit Windows: x86_microsoft-windows-servicingstack_31bf3856ad364e35_ TrustedInstaller ID _none

    For 64-bit Windows: amd64_microsoft-windows-servicingstack_31bf3856ad364e35_ TrustedInstaller ID _none

  4. Copy the subfolder name to the clipboard, and then paste it into Notepad for safekeeping.

    Screenshot of the search result of the subfolder name In the C:\Windows\WinSxS directory.

  5. Create the registry subkey HKLM\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\Version.

    Note

    To create this key, you have to be an owner of the Component Based Servicing key. Then, you have to then give yourself full access permissions.

  6. On the Version key that you created in step 5, create an expandable string value (or edit it if it already exists). To do this, use the TrustedInstaller ID as your name, and use the full path of the folder that you identified in step 3 as the value.

    Note

    In the full path, you must use %SystemRoot%\WinSxS\folder_name instead of C:\Windows\WinSxS\folder_name.

    Screenshot of an example string value setting of the Version key.

  7. Click OK, and then exit Registry Editor.

You can now start the Windows Modules Installer (TrustedInstaller) service as usual.