Windows Server: Black Screen with "Windows logon process failed to spawn user application."

After demoting a DC we were not able to get to the desktop with a black screen showing up and that was it.

Try and get Task Manager up and running produced the following in the server's Event Logs:

Log Name:      Application
Source:        Microsoft-Windows-Winlogon
Date:          6/20/2018 11:19:06 AM
Event ID:      4006
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      SERVER.DOMAIN.COM
Description:
The Windows logon process has failed to spawn a user application. Application name: launchtm.exe. Command line parameters: launchtm.exe /3 .

In the end the solution ended up being to add the local administrator account to the local Users group after hitting CTRL+ALT+DEL/END to click Log Off/Sign Out.

Once we signed back in we got to the server's desktop and were able to continue with it's removal from the domain.

EDIT: Note that the change was done from a DC via Active Directory Users and Computers.

Philip Elder
Microsoft High Availability MVP
MPECS Inc.
Co-Author: SBS 2008 Blueprint Book
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