I decided to remove MS Security Essentials based on results given here:
I want to use the free version of a program and following the results given decided to use ZoneAlarm with Checkpoint. I had some difficulties with installation (an update stopped working and the system kept hanging upon boot-up after one program tried to update automatically) but after more than a week it's been working fine.
I wanted the free version of BitDefender but there were many features missing, and for some reason AVG made my system (Win 7 64-bit) a bit slower.
How about Avast or Avira? Do any of their free versions have nag popups? There's a popup for ZA every one or two weeks (I think).
If you can recommend an antivirus with a free version that has the highest possible ratings for the three categories given in the test and no nag popups, please let me know.