Windows 10: Unable to open Windows Defender

While I was away someone tried to make changes to my system. I am trying to enable Defender, but I receive the attached message;


I am the administrator.

:)

 

WINDOWS DEFENDER FOR WINDOWS 10---UNABLE TO OPEN--ERROR MESSAGE Ox8050900c

unable to open windows defender --it is being used antivirus -no other antivirus used

ALSO WINDOWS DEFENDER OFFLINE IS NOT WORKNG

 

windows defender wont turn on

when i open windows defender red x warning saying windows defender turned off unable to turn on

 

Hi:

See here:
Windows Defender - Turn On or Off in Windows 10 - Windows 10 Forums

But the more fundamental (and worrisome) question: who accessed your system while you were away?
The reason I ask is that it's possible that this person may have made other changes that compromised your security, personal information, etc.
I'm not trying to create fear or paranoia, just mentioning it, in case you want help checking the system...

MM

 

Hi MM; I'll let you know how I made out tomorrow, after making a printout and reading all instructions. I'm not too worried about someone accessing my system - I've made an image just in case, but I will put in a password to my account. Thanks again.

 

Also, if another AntiVirus program was installed, or attempted to be installed, it could have turned off Windows Defender. I've found it usually gets restored when Uninstalling any other AV program. Sometimes have to go to Control Panel, Windows Defender to turn it on.

 

Excellent ideas.
If someone else accessed the computer, who knows what they might have installed.

If WD is disabled by Group Policy, however, would one be able to enable it merely via the Windows CP, or would one not have to reverse the GP edit or registry change?
<just asking, trying to learn>
FWIW, on my Win10 box running KIS, the WD settings are grayed out. I do not even get a way to try to enable it.
And I do not see the GP message, either, even though I am on Win10 Pro and have other GP edits in place.

So I guess my question is: when one installs a 3rd-party AV that disables WD, does it generate that GP edit message or does it just disable WD and make its settings inaccessible?

Ennywho, @benton, please let us know how it goes.*Smile

Cheers,
MM

 

I believe the installation routines make the change, mainly based on the fact the Home version of Windows don't have the Group Policy Editor [not usually needed] and in turn should change things back when uninstalled. As has been noted in many posts the uninstall routines can go awry, necessitate other procedures to clean them up.