Is it free?
No...but you get what you pay for. I'd advise staying away from Norton and McAfee as they make heavy hoof prints into your computer and are difficult to remove later. I have used both and have removed both, and have used ESET ever since with no difficulties.
However, your BEST anti-virus program IS FREE, and rests just above the keys on your keyboard... just before you strike a key...think about it.