Windows Modules Installer Error 126 - Fix

1.Make sure you have following key:

HKLM\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\Version.

key should look similar though not necessarily the same as in the example below.



2.Run Readiness Tool.Although TrustedInstaller not working this tool does not require this service.This help to diagnose damages in subfolder described by above Version key and other damages in WinSxS and CBS.This tool generate CheckSur.log file in C:\Windows\Logs\CBS folder -you have to analyze this file too.



STEP I -If you have corrupted Version key....



IDENTEFICATION CORRUPTED KEY

First you have to figure to which folder this key should correspond.General form of string in this key is following:

{TrustedInstaller ID} REG_EXPAND_SZ
%SystemRoot%\WinSxS\x86_microsoft-windows-servicingstack_31bf3856ad364e35_{TrustedInstaller ID}_none_{16 additional digits} -for 32bit system

and

{TrustedInstaller ID} REG_EXPAND_SZ
%SystemRoot%\WinSxS\amd64_microsoft-windows-servicingstack_31bf3856ad364e35_{TrustedInstaller ID}_none_{16 additional digits} -for 64bit system

where REG_EXPAND_SZ -expandable string value

In practice may be a number of folders such as above.They relate with difference older TrustedInstaller version.You have to figure which one version is currently used.
Fortunatelly subfolder in C:\Windows\Servicing\Version always have the same name as currently used TrustedInstaller version (I assigned it in this tutorial as TrustedInstaller ID)

EXAMPLES

You have following folder

C:\Windows\Servicing\Version\6.0.6001.18000

so relate string is following:

6.0.6001.18000 REG_EXPAND_SZ
%SystemRoot%\WinSxS\amd64_microsoft-windows-servicingstack_31bf3856ad364e35_6.0.6001.18000_none_657dfccc7fa7eb9a

and {TrustedInstaller ID}=6.0.6001.18000



in another axample

C:\Windows\Servicing\Version\6.1.7600.16385

relate string is following

6.1.7600.16385 REG_EXPAND_SZ
%SystemRoot%\WinSxS\amd64_microsoft-windows-servicingstack_31bf3856ad364e35_6.1.7600.16385_none_655452efe0fb810b

and and {TrustedInstaller ID}=6.1.7600.16385



and so on


FIXING KEY

1.Navigate to C:\Windows\Servicing\Version read the name of a subfolder (now you have TrustedInstaller ID)
2.Use any good file manager to find in C:\Windows\WinSxS subfolder which name starts with:

x86_microsoft-windows-servicingstack_31bf3856ad364e35_{TrustedInstaller ID} (if you have system 32bit)

amd64_microsoft-windows-servicingstack_31bf3856ad364e35_{TrustedInstaller ID} (if you have system 64bit)

write it name somwhere
3.Go to HKLM\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing (CBS),takeownership of this key and add your account to have full control.
4.In CBS key create Version subkey.
5.In Version subkey create expandable string with the same name as {TrustedInstaller ID},in Data field type: %SystemRoot%\WinSxS\{indentified folder in point 2}
6.Remove your account from permissions to CBS key and next restore ownership back to "NT Service\TrustedInstaller"



STEP II - FIXING REMAINS DAMAGES

Example.Windows Update Error 80080005 -here wrpint.dll is corrupted.This file is very important for TrustedInstaller.

Remains damages you have to diagnose and fix in the same way as for other errors relate to corruptions in WinSxS,CBS
How to Analyze the System Update Readiness Tool CheckSur.log File