DL appliance stuck with a Black Screen after logging into Windows after a RUU upgrade (4039879)

After upgrading the RUU on a DL appliance, when logging into Windows you end up with a black screen and you can't get much further. 

Processes can be started from Task Manager but the desktop user interface won't appear. 

Solution 1:

1. CTRL+ALT+DEL,
2. Open Task Manager
3. Open a New Task, type Regedit
4. Locate the below registry key
   1. HKEY_LOCAL_MACHINE\SOFTWARE\AppRecovery\Appliance or for the legacy RUU versions HKEY_LOCAL_MACHINE\SOFTWARE\Dell\Appliances\DL\
   2. Export the branch
   3. Set the value of FTBUConfigured=true
   4. Set the value of ShowSetupWizard=0  (if it doesn't exist create it as DWORD 32 bit)
5. Reboot the DL appliance

Solution 2:

1. CTRL+ALT+DEL
2. Open Task Manager
3. Open a New Task, type Regedit
4. Locate the below registry key
   1. HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell
   2. It should be:  C:\Program Files\AppRecovery\FTBU\ftbu.exe or for the legacy RUU versions C:\Program Files\Dell\Appliances\DL\FTBU\ftbu.exe
5. Export the branch
6. Change this to explorer.exe
7. Reboot the DL appliance

NOTE:  if the issue persists and the appliance was joined to the Active Directory Domain, please sign off from domain account and try to login with a local administrator, since some domain policies or damaged user profile could be causing this behavior as well.