windows defender is turned off by group policy

After upgrading my windows seven to windows 8, i had found some problem about my windows defender. Yup, my windows defender couldn't active.

just follow this two simple steps :

1. I had installed another anti virus program ( AVG ) so the windows defender was automatic turn off     by system. so the first things to do is uninstall your antivirus (skip this if you don't have another Antivirus installed).
2. The Second step is change the registry value. The Group Policy is it referring to is probably the value DisableAntiSpyware under HKLM\Software\Policies\Microsoft\Windows Defender in        the registry.Just delete that value and Windows Defender should work again..

Restart your PC and enjoy your Windows Defender.