Free Antivirus

I received a message from windows security saying Cyperdender is on but is
reporting its status to windows security center in a format that is
no longer supported and that the virus protection is incompatible.
I have been reading the posts which are very helpful and I notice
Cyberdefender is not mentioned anywhere. Should I be uninstalling
Cyberdefender and download Avast or AVG? Been using Cyberdefender for the
last 2 years and never had a problem-
.