Windows 10 How to Reinstall Windows Defender After Upgrading from Windows 7 to 10?

[maybe]

I updated an older laptop from W7 to W10. I used the media creator and the update was smooth and uneventful.

As part of my explorations I decided to remove all the metro apps using
Get-AppxPackage | Remove-AppxPackage
because I never use them

Don't know if this has anything to do with it but I notice that Windows Defender is not running and its settings are grayed out. Can't change them. See attached images.

And when I tried to download Windows Defender, a popup appears asking me to register my windows or enter the registration key. This is an upgrade from a legit Windows 7 that used to run Defender.

How do I reinstall Defender? Where do I find the registration number it wants? Why do I need to "purchase" it? Thanks.

 

[maybe]

Additional information:
I downloaded WindowsDefender.msi but when I tried to run it a popup said I didn't need to install Defender because it was included in "vista" and didn't give me the option to install it.

If it is included why can't I change the settings in the images above and why do I get a popup saying WD is not running?

(I do have Avast running if that is relevant).

 

[kemical]

(I do have Avast running if that is relevant).

This will disable Defender. Uninstall Avast and Defender should pop back.

 

[maybe]

Can't I run both in W10?
I do in w8.1.

 

[kemical]

Hmm... I think it depends on which AV it actually is. Some will run alongside Defender and others will disable it. (I think)

 

[maybe]

You are correct. I checked my 8.1 laptop and Windows Defender was turned off there too because I have Avast running. I had wrongly assumed Defender was on because Windows Update regularly downloads Defender updates. Wrong assumption.
Thanks for the help. Sorry to have troubled you.

 

[kemical]

Not a problem Maybe. Glad to help..