I am using AVG (Free) for several years on my home computers. In addition, I am installing AVG Free on computers of my family and friends.
But none anti-virus can offer 100% protection (because new unique variants of infections are released every moment and virus makers are trying to by-pass known detected variants to be not detected for some time, when released). I recommend to think twice before clicking (trusting/downloading/running) any file from Internet. And to keep everything on your computer updated (operating system, anti-virus, internet browser, plugins/add-ons, etc.) to minimize misuse (exploit) of possible security hole.