If you are running Windows XP, uninstall the whole Norton package, then install AVG (Anti-virus) and Comodo Free Firewall.
AVG Free : click here
Comodo Free Firewall : click here
Although Comodo will require a little setting up, it is pretty simple to understand.
If you're using Vista, then you can either use the built in Vista Firewall or Zone Alarm Free Firewall.