I run a mail out list of over 90 users of AVG free. I have used paid for Norton (too invasive and too much of a resource hog...slows down less powerful computers) and paid for MacAfee (OK but still invasive). I never use a firewall and just have AVG and MS Antispy + a bit of common sense. Result = no viruses, trojans or worms. The other 90 people on the list have never had a problem. Make of this what you will.