In my past experiences Norton is not a good program to use, simply because when Anti-Virus programs become too large they begin to lose their effectiveness and become counter-productive. Norton is a very large program for it's purpose and if you install norton you might as well just be downloading a virus.
The other problem with well known programs like norton (Especially paid programs) is that they are big targets for virus work-arounds.
I used to use AVG for this very reason. It was a considerably small program and did it's task well and was not a well-known anti-virus program which reduced work-arounds to virus protection. (I've caught viruses with Norton multiple times, if you're buying a subscription you're seriously wasting your money.)
AVG got too big, like norton, to fulfill it's purpose though.
Currently I'm using Microsoft Security Essentials. It's a free program distributed by Microsoft and is pretty user friendly. Fairly small program, not heavy on resources but very powerful protection, not had a problem with viruses since I installed it. :D
"Balancers are 10 a penny"