Windows 10: Cannot remove Windows Defender Tray Icon

If I manage to delete the entry before the program is supposed to start up, it won't start. Is there a way to automatically delete the key whenever windows starts? Or, could I possibly make it so that key can only be written to by me?

 

I managed to fix it. If you change the Run key's owner to yourself and remove all other group permissions, the entry can't be written, and it won't launch on reboot. Thanks, everyone.

 

That may have unforeseen consequences for the system, especially if anything else needs to add an entry to the Run key later on.

As I said, killing the UI task makes the icon disappear. A much safer approach would to be to leave the ownership and permissions of the Run key as it should be - you just have kill the task at start-up. You can do this for your user account by putting a .bat file in the folder:
C:\Users\<your_username>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
containing the command:
taskkill /im MSASCuiL.exe

For all users you could put it in:
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp

I've tested this, the Defender icon briefly appears then vanishes again. Put the Run key back as it was before the system breaks *Smile

Actually, there's an easier way to remove the icon for all users, just disable 'Windows Defender notification Icon' in Task Manager's Start-up tab. Apparently you may not see it there. I do, but then I also see it in CCleaner. You said...

Maybe this is am unintended side effect of other registry changes you tried before posting here?

 

Genius, thank you!