virus.....virus....everywhere

Its really getting difficult with these computer viruses. oh what a headache. it is exactly one year before we had to format our computer for virus infection and retreive the data. now again there is the same problem. i had installed AVG antivirus free edition it was working nicely only but after one year it started to tell me to load new version and the new version has to be purchased. that's ok but the engineer who came for formatting tells that AVG is useless. there are a variety of advices from differnt people. i am really confused and could not find out any route. i feel that these viruses are created by the anti virus companies and they make us buy any antivurus software so that they will have good sales. if that is how they are selling then surely these people have to suffer one day.