Hello schneem4.
There's no best protection, so to speak. Norton is a popular software choice no doubt; but in my opinion, free anti-virus programs such as AVG Anti-Virus does the job equally well, if not better.
You may also require anti-spyware programs such as Ad-Aware and Spybot S&D as recommended by MadGamer.
And if you do decide to get rid of Norton Internet Security Suite, you will also require a good software firewall. I have a Firewalls FAQ here that may serve as a good read:
http://www.pchelpforum.com/firewalls...walls-faq.html
Besides Comodo as MadGamer suggested, I would also recommend that you try out ZoneAlarm, which is yet another free, excellent choice.
Let us know how it goes!