Windows Defender not working after upgrade to Windows 8.1

I have Windows 8.1 x64. This was upgraded using the AppStore update from fresh install of Windows 8 x64.

When i turn on windows defender from security center, it just opens the system32 folder.
If i try to turn on the defender service, i get a 577 error as shown

How can i reinstall defender?

(I was using Comodo Internet Security while the upgrade happened but now i have uninstalled it).
Thanks Prakash,

I already tried that, should have mentioned in my question earlier.
Sfc finds no errors.

As for the Referesh & Rest option, i am afraid i will loose my office installation activation and it may not work again.

I resolved the issue by following using help from some other thread from these forum using these instrucitons:
I opened up regedit and navigated to the policies for Windows Defender. Changed the permisssions for this folder and added administrators to it.
Then i changed the two entries (DisableAntiSpyware and DisableAntiVirus) to "0" instead of "1".
Then i manually opened the "MSASCui" from "C:\Program Files\Windows Defender" and Defender opened :)

Now i am thinking if there woud be any negative effects of changing permissions of that registry folder and the values as stated above.

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Question Info

Last updated March 9, 2020 Views 16,436 Applies to: