I don't like Norton one bit, nor am I a fan of MacAfee. I run Trend Micro's products on our servers as well as on desktop computers. As a server solution Trend Micro is fast becoming a force, with a large number of ISP's using it too.
As a desktop solution, Trend Micro's PCCillin leaves the least amt of footprint on a system, I compared it with Norton as well. That includes registry entries and unuseables.
They even have a very useful online scan tool.
And on dealing with in-the-wild virii, I've found that our PCCillin running comps get updates much faster than Norton sends em.
In other comparisons, the antivirus itself is $10 USD cheaper than Norton.
Pattern & Engine Updates are by itself wayy smaller than Norton [2.4MB vs ~800K].
And the most annoying of Norton, is that it is Symantec through and through - proprietary!
On another note, if your engines are old, Norton has a bad bug in the POP scan! That doubles as a vulnerability.
To add to GLC's 'cellent writeup, I gotta add the following as the Zeroeth law perhaps [thermodynamics anyone?]
The first defense you have against virii, trojans, hacks etc etc are:
COMMON SENSE
Avoid warez, crackz, gamez and other suspicious sites and software, it'll eventually catch up
If you have a doubt about something dont run it. If the email source was in fact addressed to you, or if your antivirus gave in a warning and you badly badly need that file, run it through at least 2 different anitivirii. No it doesnt mean having to buy them, there are a lot of options, like http://housecall.antivirus.com/ or simply forwarding the file as an attachment to a yahoo or hotmail email account and trying to download it from there.
Do not run any servers any longer than you need them, FTP Daemons etc etc, are easily taken down.
Do not respond to spam mail, its just a confirmation of your mailboxes' existence
Be aware of the risk that you entail with any gateway software. Anything that opens a port is potentially at risk, so try to read up whether the current version of the s/w u are running has any vulnerabilities that the developers are addressing. Good sites are aplenty starting from Google to Packet Storm
If you are a system administrator, download a port scanner and scan your ports yourself.
Do the simple things, like looking through preference menus of various software you may run.. for example if you have Yahoo, look in the preferences and say YES to Do not Reveal IP address. If you're using ICQ, set it to send messages through the server ALWAYS. Only chat with people you trust. [The reason being that if you sent even a msg through a direct connection, it takes longer PLUS invariably your IP is transmitted thru]
Always use a proxy server if you have a static IP, your ISP has a provision for it, not just for speed but also for concealing your internet identity.
Remember, software like antivirii, port blockers etc etc only go so far, ultimately it is usage trends that bring the system down.
Cheers