Norton is the most bloated POS software ever made. Do like jaross said and download the free version of AVG. It is updated at least once a week, uses minimal system resources, and it just great. I've been using it for the past 3 or 4 years and have not once had a virus, its good stuff. Be sure to use SpyBot and AdAware along with it to keep your comp running good.
And if you want/need a firewall Kerio and Panda are both awesome. Again, Nortons is a resource hog, it does its job but at the exspense of making your computer a slow POS.