On Black screen:
1. ctrl+Alt+del
2. Start Task Manager
3. File-Run-regedit
The fix is simple and easy
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell
Delete the Shell key and then recreate it as a REG_SZ key
Like:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
“Shell”=”explorer.exe”