Symantec, forget it, it is much too tough on ressources, slows down any computer like you feel to upgrade all the time. It lets too many things go through anyway. I think it has great reviews just because they spend a lot on marketing and reviewers just can't say it so-so, otherwise they just could loose revenues.
Try Avast, its free for home use, the same as AVG which is also good.
Avast has never let anything either in or out, it even has a script blocker contrary to AVG. It upgrades by itself etc, etc. It even talks to you, if you feel lonely... :x
For free, its the best out there, no question about it. For the money, the best is Nod32. I have tried many of those and just don't take my word for it, try !