Windows Defender service does not start
I had an issue in Build 10041 of the Windows 10 Technical preview where the Windows Defender service would not start because of previously installed Antivirus software (F-Secure Client Security 11.51 build 101).
Bear in mind that services such as Windows Defender and Windows Firewall will automatically turn themselves off when you install Antivirus or Firewall software. This is by design to avoid conflicts.
If you don’t fall into the above category please read on.
Fortunately the fix is very simple and can be found here:
To remove the annoying popup simply delete the following key:
Make sure you backup your key just in case you would like to restore it.
27/04/2015 – Remove Windows Defender not running pop-up