Could you please give us more details about the issue? Is this a booting problem? Is the PC booting normally or you only see black screen with no icons and no task bar? In that case, try pressing CTRL+ALT+DEL and check if the Task Manager will open. Search for the explorer.exe and end the process. From New, create a new process, typing explorer.exe in the line. Press OK and check if there will be any change. If not, use a Windows installation drive and the Repair option.