Unless you are going to lots of 'bad' sites personally I think all the extra programs and antivirus stuff will actually slow the computer down. I just stick with microsoft security essentials never have an issue.
Absolutely agree, and Norton is by far the worst.
Another bit of advice: I never click on a link in an email that someone has sent, even from someone I know. Sorry friends, but those "must see" and "gotta watch this..." emails with links to unfamiliar sites are immediately deleted. Not worth the trouble they could potentially create.