Well you ma ywant to justy OUST NOrton all together.
While Norton is the most popular RETAIL AntiVirus solution, it is also one of the most problematic solutions available. Even when it is running nice, it still slows down the system from it's unresourceful nature.
For a home PC, we've had this converstain ere SO many times, the general concensus is to use AVG AntiVirus. It is free, updates JUST as any other does, offers EXCELLENT scanningor boot, system and email. It is VERY unoctrusive, you never see an error or have it crashing or hanging up other programs,it just sits there and works.
Don't fool yourself into thinking retail options are the best, just look at Windows for that answer!
You can get a copy of AVG FREE Edition here, http://www.grisoft.com
Just run your NOrton Add/Remove programs applet and you can uninstall JUST the AntiVirus posrtion of it and still leave other aspects of the progrtam ou like installed.
Then install and update AVG and you're done!
That's what most users here use at home anyway, I always remove Norton from client PC's and replace it with AVG too, rock solid every time.
You will forever be thanking yourself for doing it.