There is no MSE in Windows 8, it is not compatible in Windows 8 that’s why Microsoft merged MSE with Windows Defender, now Windows Defender offers same malware protection as that of Microsoft Security Essentials. If you want to install another antivirus in Windows 8 Windows Defender automatically backs away, so you don’t need to turn off or disable it manually but however if you want firmly to disable Windows Defender, here is how to do it.
Turning off Windows Defender in Windows 8
1. Start typing as metro search Shows “Windows Defender”, open it by double clicking on it.
2. Now select Settings tab in main window of Windows Defender and select Administrator on left, on right pane uncheck or remove tick mark for “Turn on Windows Defender” and click on “Save changes” button.
3. Now Windows Defender has been tuned off, now Windows starts warning that Windows Defender has been turned off and asks to check another antivirus installed status in action center. You’ll get alerts from the system tray also to turn on antivirus protection.
4. Now you can install any other antivirus that is compatible with Windows 8. We’ve learned that after uninstalling third-party antivirus, Windows 8 automatically enables Windows Defender after system restart which avoids user’s action of turning on Windows Defender and its good for users from security point of view.