avast
do they still have those annoying popups?if so no
if you register you do not get warnings popups.and you should still be able to disable them anyways.
is registering free?
Microsoft Security Essentials.
If you want a high-quality antivirus, I would suggest BitDefender of Kaspersky.EDIT:Ill just leave this here so you can decide.
Don't you get a virus every other week?