What can I do if I can't start Windows Defender after upgrading Win10?

Windows Defender is Microsoft's built-in anti-virus program. Many Win7 users have upgraded to Win10 system and found that Windows Defender can't start. What is going on? In this case, it is likely that the user has used MSE before, although under normal circumstances, after upgrading Win10 system, MSE will be cleared, but there are also cleanup conditions, which leads to Windows Defender startup problem, then How to solve it?

as follows:

a, remove remaining MSE

1, is positioned below the path to the file Explorer:

1. 01
   C:\\Program Files\\Microsoft Security Client\\
   
   Copy the code C:\\Program Files\\Microsoft Security Client\\

   2. Right click on the Setup.exe file. Select Attribute → Compatibility & Rarr; Change settings for all users;
   

   3. Check "Run in compatibility mode", select Windows7 from the drop-down menu, click “OK& quoquo;Save;
   

   4. Run the command prompt as an administrator and execute the following command:
   

   1. 01
      C:\\Program Files\\Microsoft Security Client\\setup.exe /x /disableoslimit
      
      Copy code C:\\Program Files\\Microsoft Security Client\\setup.exe /x /disableoslimit
      

      5. After the command is executed, select “Uninstall” to restart the computer.
      

      Second, restore Windows Defender service
      

      1, enter "ldquo; service" in the Cortana search bar, press Enter to enter (can also run services.msc in the run);
      

      2, to see whether to disable Windows Defender-related services, and disabling it may try to enable, as shown below;
      
      

      3, can also run the command prompt in administrator mode, execute the following command To start the service:
      

      1. 01
         sc config WinDefend start= auto
         
      2. 02
         sc start WinDefend
         
         Copy code Sc config WinDefend start= autosc start WinDefend

         Note that if a third-party killer is installed on your computer, Windows Defender will not start by default.
         

         The above is Win10 can not start the Windows Defender repair method, more methods can refer to: "Windows 10 system Windows Defender can not start the repair method"