AVG Antivirus is the one to use. I have used , trend micro cillan , norton , mcafee , virus dr. and bitdefender.
AVG is best out of all the antiviruses except for Bitdefender. If you don't mind spending some money on your antivirus program then Bitdefender is definitely the best . It has been rated the 1 antivirus out of all the antiviruses.
The rating has been done by PC WORLD MAGAZINE , the following link shows these ratings
However if you don't use the internet heavily and you don't have such important data on your pc then go with AVG , since it is free and has fairly solid protection. I use AVG since i don't have anything important on my pc.
You can find AVG from the following link