how do I reinstall windows defender for windows 10

ALL THESE PEOPLE WITH BASICALLY THE SAME PROBLEM TURNING ON WIN 10 DEFENDER AND NOTHING BUT BULL ANSWERS (IF ANY) FROM MICROSOFT. WHAT ELSE TO BE EXPECTED. CAN'T EVEN REMOVE IT FROM MY PC NOW EITHER, NEVERMING GETTING IT TO WORK!!

I have exactly the same problem - but I haven't found any answer posted. How do I get windows defender turned back on?

Hi Lucy,

Welcome to Microsoft community.

• How did you uninstall Windows Defender?

Please follow the below steps and check:

 Step 1: Enable Windows defender from control panel 

1.    Press Windows + X, Click on control panel.

2.    On right top corner click on View and then choose large items.

3.    Now from the list click on Windows Defender and try to enable it. 

If not try to enable it from services. 

Step 2: Enable Windows defender from services.msc. 

1.    Press Windows + R, to open run prompt.

2.    Type services.msc and press enter to open services list.

3.    Under services look from Windows defender service and start the service.

If you face any issue while troubleshooting, please provide the outcome, so that we can work on your issue. 

Hope the information helps, if you have any further queries, feel free to post. We are here to assist you.

Rehards,

Guru Kiran

error 577

windows defender cannot be enabled

because of the above error

it seems like there is some new malware that turns windows defender off.  even when everything else is cleaned out it won't turn back on.

says the app is turned off by group policy

Do you have any online reference to this malware or its source? I get the message "not a valid Win32 application".  Also, I could not start the Windows Defender service (Error: 193: 0xc1)

This occurred after my last comprehensive update of Windows 10 was installed.

If you have Defender  & have Viper for Antivirus Can you keep Defender