Norton is a good program but you will find what one finds another program will not, my self you have it installed I would keep it, just check for updates and run scans. If you want to remove it you can and here is a link to a free one, but make sure you remove Norton first as two AV programs are overkill and not recommended. Keep in mind also that AV programs find and block viruses and not a lot of the malware floating around.
Free Anti Virus Programs
A Firewall also should be installed, these are all free
Java Runtime Environment (JRE) 6 Update 6 <-- You should have installed this and you can remove all the other ones that you see in the Add Remove Programs.