Norton is by far one of the worst antiviruses out there. Not only does it too a terrible job at catching viruses but it's invasive and takes up way too much RAM IMO. Even after a complete uninstall, your registry will still have Norton in it. And I don't just mean, 'history' or 'footprints' of the program. I'm talking about data that Norton installs without the users knowledge. IME symantec, Macafee and all it's chums are just as useless.
If you're looking for something effective, quiet, and that doesn't use up tons of memory I HIGhLY recommend ESET NOD32 or Kaspersky. Don't waste your time or money on the rest.
+1 I hate Apple