Windows Defender in Windows 8.1 Will Not Turn On

Hi Michael,

It would be great if you can provide more information regarding this issue. Please answer these questions for a better understanding:

1)       Are you able to open Windows Defender program on the computer?

2)       If yes, what exactly happens when you turn it ON from its user interface? Do you get any error message?

I would suggest you to try the following methods and let’s know the results.

Method 1: Start the Windows Defender Service Manually

Please follow these steps:

 a)       Press “Windows Logo” + “R” keys on the keyboard to open the “Run” command box.

b)       Type “Services.msc” in the “Run” command box and press “Enter”.

c)       In the “Services” window, search for the “Windows Defender” service from that list.

d)       Double-click on it to open its “Properties” window.

e)       From its “Properties” window, click on “Start” when the service is stopped and also change its “Startup Type” to “Automatic”.

f)        Click on “Apply” and “Ok”.

g)       Restart the computer and check if that resolves the issue.

If the issue still persists, then try the next method.

Method 2: Run Windows Defender as Administrator

a)       From the Windows 8 Start Screen, type “Defender”. Windows Defender should appear in the list.

b)       Right click on the “Windows Defender” icon and select “Run as Administrator” from that menu.

c)       Check if that launches Windows Defender on the computer and check if you are able to turn it ON.

Please get back to us with the results.

I have the same problem - I tried both of your methods & received errors - unable to send screen shots due to word count

I have exactly the same problem as above. I am unable to turn on Windows Defender. When I try method 1 to start it manually I get

Windows could not start the Windows Defender Service on local computer.

Error 577: Windows cannot verify the digital signature for this file.  A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source.

I was unable to start Windows Defender when I bought this laptop new a couple of months ago. It simply would not turn on. Then I updated from Windows 8 to 8.1

The Lavasoft antivrius I had installed (when I found Defender would not work) to protect the laptop would not work any more with the update to 8.1

So I uninstalled and reinstalled Lavasoft but it still would not work so I uninstalled it again.  My laptop is now currently unprotected apart from the free version of Spybot Search and Destroy 2.2 which is the only thing I can find that seems to work with Windows 8.1

There appears to be almost nothing that works in the free antivirus protection now, your Microsoft list says most stuff is incompatible or unknown.

I would very much appreciate some help here to get Windows Defender to work, or please could you point me in the direction of some free antivirus software that will work. Or give me some plan whereby I can protect my computer.

To prevent software conflicts, performance issues and reduced efficiency of the affected antimalware programs, Windows Defender is disabled on Win 8 when third party antimalware programs are installed on Win 8.

When you purchased the laptop it probably had a trial version of an antivirus program installed.  Did you uninstall that program and use the appropriate software removal tool and then reboot the computer?

List of anti-malware product removal tools

Recommend you thoroughly review  

Windows Defender on Windows 8 - Introduction and Frequently Asked Questions

Did you use the Lavasoft Removal Tool?  If not suggest you run it and reboot the computer: http://www.lavasoftsupport.com/index.php?showtopic=28

I have not used Lavasoft in many years and know very little about it - do not know when it will be compatible with Win 8.1.

You may need to restart the Security Service and then enable Windows Defender after removing Lavasoft.

For further information about antimalware products see the following:

http://www.dslreports.com/forum/r28298407-2013-Anti-Virus-Poll-

http://www.av-comparatives.org/

http://www.opswat.com/about/media/reports/antivirus-august-2013

And

See the following compliments of quietman7 MS MVP: **Choosing an Anti-Virus Program**

Regards....

Thanks.

Yes the laptop had Norton Antivirus on it when I bought it. I knew I wanted to used Defender so uninstalled it immediately and I did use a software removal tool.

But Defender still would not turn on.

This was when I installed Lavasoft as I have used it for a long time on my old laptop which was an XP and I was happy with it.

But as I said I installed Windows 8.1 and then Lavasoft wouldn't work any more. I uninstalled it but didn't use the removal tool that time.

It looks like I should try one more time with removal tools for both Norton and the Lavasoft, using your links

I will see what happens, and if I still cannot turn Defender on, then it is going to have to be something else to use to protect my laptop.

Thanks for all the other links. They are very good, and thanks for responding.