Hforman gave a great response, but I also have to agree with the follow-up to that, and please don't use Symantec. They've gone from great software to greater bloatware, and do a lot of things we don't really need, and slow the computer in the process.
For the last 9 years now, I've been running Avast Av software - the free version - and recently they dropped a new business package that is also free if you meet certain limitations. I will say that before I installed the business version I didn't get a single advertising e-mail from them. That's a huge thing to say about an on-line company. They're not based in the US, which has some people squirming, but I still feel that's OK. Since the upgrade to the business version, I get daily e-mails telling me how many threats were blocked, and which systems they were blocked on. I'm OK with these, as it also keep my head in the game and allows me to tailor the blocking on the systems.
I also use multiple add-ons for my browsers to stop automatic scripts.
NoScript is an awesome addon, and once you spend the initial time configuring it, you'll find a lot of sites use the same sources for data, so you don't have to fully configure for every site. Once configured, it sits quietly in th background helping keep you safe.
Adblock Plus helps stop all those little ads that may be intrusive, and there's a free filter source they provide that you can use to turn on non-intrusive ads. I have those on - since sites can actually make money on just serving those ads to me. If they're making money on it, then they're more likely to stay open.
One thing Avast provides in the list of google hits is a little icon next to each link telling you if the site is safe or not. I find that comforting, but still don't trust any of them right off the bat, and manually control the scripts allowed.
Good luck,
Scott