Ignore re-installing it. If you read the pages on here you'll find my myself and many others see it as being one of the worst pieces of software you can install on your PC. It slows it down, and isn't even the best at detecting viruses.
Far better are free alternatives, such as AVG, zonealarm and ad-aware (comprising anti-virus, firewall and anti-spyware, respectively).
So I suggest you install these things instead. But before doing that, properly remove Norton (as I say, it's a terrible program and doesn't even uninstall itself properly).
1)
norton removal tool
2)
AVG
3)
zonealarm
4)
ad-aware