Some false internet security program started to run. My husband didn't close the window properly (I guess) and MSE stopped working. I did a restore point first. The restore succeeded but MSE still didn't work. I tried to uninstall and reinstall MSE. Couldn't do it in the typical manner (programs > unintall). So I downloaded Malwarebytes which found and removed some trojan. Still couldn’t uninstalI MSE. I was finally able to remove MSE using Microsoft article at support.microsoft.com/kb/2483120. But I have not been able to reinstall MSE. I even removed Malwarebytes in case it was the problem - conflicting AV software - even though I run both on my other computer. Then I went through all the steps in windows.microsoft.com/en-us/windows/i-cant-install-microsoft-security-essentials. Error code is 0x80070643.
One answer in this forum told me that maybe I needed to run updates in windows. I can't run updates either -- I think that error code was 0x80070002. Even the windows update troubleshooter couldn't fix it.
Any help would be greatly appreciated.