Add a Custom Script to Windows Setup --

 

Windows setup scripts

Setupcomplete.cmd and ErrorHandler.cmd are custom scripts that run during or after the Windows Setup process. They can be used to install applications or run other tasks by using cscript/wscript scripts.

• %WINDIR%\Setup\Scripts\SetupComplete.cmd: This script runs with local system permissions and starts immediately after the user sees the desktop. This setting is disabled when using OEM product keys, except on Enterprise editions and Windows Server operating systems.
• %WINDIR%\Setup\Scripts\ErrorHandler.cmd: This script runs automatically when Setup encounters a fatal error. It runs with local system permission.

https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/add-a-custom-script-to-windows-setup?view=windows-11