I liken Norton to the 'Bloke down the pub', he thinks he knows everything and can do everything. Poeple are always talking about him as if he's special. But when it comes to the crunch turns out to be completely useless!
AVG, or Avast if you want less interferance in daily use.
I have found Norton to be very resource intensive: if you don't believe me then look at the task manager and see how much memory Norton processes such as NAVAPSVC.EXE use. I prefer the free AVG and am very happy with it (especially the price :>) ).
AVG Free is brilliant. But make sure you also have a firewall running, as well as some sort of spyware program. Personally I go for Kerio Personal Firewall and Ad-aware Personal spyware protection (both free)
i used too have avg but i had way to many anti viruses anyway so i now just have mcafee (which is useless and came free with the computer) and avast! which is very good
lamb balti: I'd recommend just using one. Using more than one sounds great, but they can interfere with each-other and cause problems. One should be more than enough.