Les, I've been programming PC's for decades in multiple language, running Linux servers for over 10 years, and can rip memory resources, networks, etc into tiny fragments.
Norton is still basically not the best. CNET provide the industries standard accepted reviews and they agree with me http://reviews.cnet.com/antivirus-an...-33770771.html
Out of all of them Avast comes out the best http://download.cnet.com/Avast-Free-...-10019223.html .....and it's free!