Running Windows Defender the first time after re-enabling it in the registry You have to be logged on as an Administrator to change this field, restricted users can only view the current value. Changing the 1 to a 0 was all that it took. On the computer with Avast installed, it was 1. If it is zero, then Windows Defender can run free. The critical registry key is DisableAntiSpyware. HKey_Local_Machine\Software\Policies\Microsoft\Windows Defender In brief, the fix was to run regedit and navigate to
The solution that worked for me (Windows 7, 64 bit) was documented here: How to Fix Error Code 0x800704ec when Turning On Windows Defender. The article offers three solutions, I used the one that updates the registry, but, of course, not until I made a Restore Point. Despite the error message from Windows, Avast had not used group policy to disable Windows Defender.
Online searches turned up assorted suggestions for configuring group policy, but that wasn't my problem.
