I recently removed a security suite from my PC. Windows Security Center continued to recognize its presence. This wonderful & easy fix revealed what was actually running & alleviated doubt that I might, albeit asymptomatically, be in fact running two AV/FWs. I was given this by an Avast forum moderator "Tech" & in turn want to share it with you. I used it today while a Microsoft tech was on the phone with me! Microsoft now has a fix for its software!
You'll want to do this in Safe Mode without Networking.
1) Go to the Control Panel & open Administrative Tools.
2) Click on Services.
3) Go to Windows Management Instrumentation & Stop the service.
4) Stop Security Center Service too.
5) Let them Automatically start.
6) Exit out to the desktop, click Start, & choose Explore.
7) Go to C:\windows\system32\wbem\repository.
8) Delete this subdirectory (the repository folder only!).
9) Exit & reboot. (You may need to reboot twice.)
This will rebuild the deleted folder & the database. Windows Security Center should show the correct information. Voila! The AV & FW should be recognized.