AVG is good, but I perfer
ClamWin myself.
Symantec products are now all viruses themselves. Their shitty anti-virus (and other, useless products) install themselves so deep you can never 100% purge them. They wrap their tendrils around many other pieces of software too. Suddenly there will be a button in your browser, your word processor, Explorer. Every file you download gets a pop-up "This is clean and I'm annoying" and "Don't forget to pay for more of our shit".
They're spammy, they're destructive and they have, on occasion, been directly responsible for the whole computer to end up fucked.
I also like
Adaware and
Spybot.