Windows 7: Cannot Install Microsoft Security Essential, error 0x80070645

Hello,

My problem is with Microsoft Security Essential (MSE). I had some problems with Security Client while installing windows updates, which causes the updates not to be installed. Searching the Internet, I found that I have to re-install MSE. I tried to uninstall it. I got error about (epp.msi) cannot found, so I used "Let me fix it" tool from Microsoft to uninstall it. Succeeded to uninstall it, I tried to install it again; however, I got Error 0x80070645 [attached the pic.]



I hope you can help. Thanks,

Did you try restarting your computer?

yes

Have you followed this Microsoft knowledge base article?
Error: 0x80070645 appears when you try to upgrade Microsoft Security Essentials

Yes, I did. I have searched Microsoft web site, tried many solutions but did not work.

Make sure you don't have any other anti virus programs or 3rd party firewall blocking MSE.

Something I read in an article a while back said that if you are already infected with a virus, MSE may not install. It might be wise to run a scan with Malwarebytes or another AV Scanner (SuperAntiSpyware, Windows Defender Offline) just to confirm your system is clean.

Also, as Layback Bear mentioned, do you have any other AV's or Security software installed on your PC?

I did a scan and found nothing. I have only Malwarebytes installed only right now. And MSE was the first antivirus in my PC

Make sure it's totally uninstalled Uninstalling MSE - Microsoft Community

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