I just don’t think there is any ONE thing.
Norton is good if it doesn’t mess up your Outlook Express. It is quite comprehensive, and if you insist on relying on any one thing it’s likely the way to go.
I also run Aluria, which cost me some 30 bucks a while ago. It monitors if you are being jumped by trojans etc. I run it once a week to clean out accumulated messes – and while I am very safety conscious and don’t download stuff it always finds a bunch of messes. It was also the only program, (I tried all the free anti spyware ones) that rid me of a very nasty trojan.
And for a firewall I prefer Zone Alarm Pro. It gives you full control and is just the best out there.
Since Norton does mess with my mail in a bad way, I use Macafee. The only complaint I have there is the graphic it displays when it catches a bug – a hand squeezing the life out of a bug – YIKES!!!!