Windows 10 windows defender not turning on, no other anti-virus installed

Hi Mazuren,

Thank you for posting your query in Microsoft Community.

I understand the inconvenience caused to you. I will be glad to assist you with the Issue.

I would suggest you to follow these steps and check if it helps:

1. Press Windows Key + R
2. Type regedit in the run box.
3. Locate the following path *HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WINDOWS DEFENDER*
4. Right click this file and select permissions
5. Press Advanced
6. Where it says owner press change
7. Change the owner to your username
8. Now press apply then ok
9. Select Full Control from the permissions menu

(click the Widnows Defender folder)

10. Find the value DisableAntiSpyware and DisableAntiVirus and set these values to 0

(explaination: double click each and where the 1 is put 0 and press ok)

11. Open services.msc
12. Find Windows Defender
13. There should be 2 services: Windows Defender Service and Windows Defnder Netwrok
14. Right click each and press start
15. After you have started both restart your computer
16. Run Windows Defend er

For reference How to protect your Windows 10 PC

http://windows.microsoft.com/en-us/windows-10/how-to-protect-your-windows-10-pc#v1h=tab02

Let us know if the information helps. For further assistance feel free to post your queries in Microsoft forums. We will be glad to assist you.

Thank You.

still refusing to start

tried a bunch of ways to start it. when i tried to start it from the windows defender program i got error code 0x8007139f

Hi Mazuren,

Thank you for posting your query in Microsoft Community.

I understand the inconvenience caused to you. I will be glad to assist you with the Issue.

I would suggest you to follow these steps and check if it helps:

1. Press Windows Key + R
2. Type regedit in the run box.
3. Locate the following path *HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WINDOWS DEFENDER*
4. Right click this file and select permissions
5. Press Advanced
6. Where it says owner press change
7. Change the owner to your username
8. Now press apply then ok
9. Select Full Control from the permissions menu

(click the Widnows Defender folder)

10. Find the value DisableAntiSpyware and DisableAntiVirus and set these values to 0

(explaination: double click each and where the 1 is put 0 and press ok)

11. Open services.msc
12. Find Windows Defender
13. There should be 2 services: Windows Defender Service and Windows Defnder Netwrok
14. Right click each and press start
15. After you have started both restart your computer
16. Run Windows Defend er

For reference How to protect your Windows 10 PC

http://windows.microsoft.com/en-us/windows-10/how-to-protect-your-windows-10-pc#v1h=tab02

Let us know if the information helps. For further assistance feel free to post your queries in Microsoft forums. We will be glad to assist you.

Thank You.

I got lost at step 10.

I really don't know what else can I do, my computer is not protected. I've tried to do it with avast, which was constantly saying - you are protected, and that there are no viruses etc. But when I started boot time scan it found a lot of viruses, some of them in Windows folder, C partition, and moved it all to chest. After that I've uninstalled avast, and tried everything again and again to get Windows defender running, but nothing happened, still not protected. 

Did you completely remove Avast?

Wiki article: List of anti-malware product removal tools

Are you sure that the infections are completely removed?

Try Malwarebytes Antimalware (free version, do not install the trial or Pro version) - http://www.malwarebytes.org/products/malwarebytes\_free/

Try SuperAntispyware Free version - http://superantispyware.com/download.html

Try the ESET free online scan:  http://www.eset.com/us/online-scanner/

Try the Microsoft Safety Scanner:  http://www.microsoft.com/security/scanner/en-us/default.aspx

You could go with a 3rd party antivirus program:

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

Or you could bite the bullet, back up your data and --

Restore, reset, refresh Windows: http://windows.microsoft.com/en-US/windows-8/restore-refresh-reset-pc or

http://www.groovypost.com/howto/windows-10-reset-your-pc-feature/

-steve

Hi Mazuren,

Thank you for posting your query in Microsoft Community.

I understand the inconvenience caused to you. I will be glad to assist you with the Issue.

I would suggest you to follow these steps and check if it helps:

1. Press Windows Key + R
2. Type regedit in the run box.
3. Locate the following path *HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WINDOWS DEFENDER*
4. Right click this file and select permissions
5. Press Advanced
6. Where it says owner press change
7. Change the owner to your username
8. Now press apply then ok
9. Select Full Control from the permissions menu

(click the Widnows Defender folder)

10. Find the value DisableAntiSpyware and DisableAntiVirus and set these values to 0

(explaination: double click each and where the 1 is put 0 and press ok)

11. Open services.msc
12. Find Windows Defender
13. There should be 2 services: Windows Defender Service and Windows Defnder Netwrok
14. Right click each and press start
15. After you have started both restart your computer
16. Run Windows Defend er

For reference How to protect your Windows 10 PC

http://windows.microsoft.com/en-us/windows-10/how-to-protect-your-windows-10-pc#v1h=tab02

Let us know if the information helps. For further assistance feel free to post your queries in Microsoft forums. We will be glad to assist you.

Thank You.

I have problems with this. I've done everything that you said, but got stuck when I came to steps 10 and 11.

Apparently, when I'm supposed to do sStep 10 - I can only find DisableAntiSpyware, there is no DisableAntiVirus value, and steps 11, 12 - There is no Windows Defender in services.msc

any help???