Normally, I would get Norton and run it for one year, let it expire, and just run it for about another year (without updates)... Then look for a good sale.
I get very few (i.e., none in the last 3-4 years) virus email notifications from Norton (I tested with a test virus and it does work--I guess I am not getting any viruses). I know that Earthlink was filtering viruses for awhile (used to get notification--check your IP and see if they do... Also, some IP offer free anti-virus downloads).
The port scan warning is just a "sales tactic" to scare you into purchasing their product. Yes, there is a lot of port scanning going on and you need a firewall to help keep you safe (if you are running windows). Norton's firewall keeps running even if updates expire (I believe).
Look at
www.grc.com and try "Shields up"--he has a nice firewall test and talks about the various options.
Windows firewall will work to protect against inbound problems. ZoneAlarm and NIS also protect against outbound problems too (such as you get a virus or other problem and it tries to access the Internet--ZA and NIS will ask you if you want to give the program access--AFAIK Windows Firewall does not support this feature).
I am also using Firefox (browser), Thunderbird (email), Spybot Search and Destroy (anti-spam for IE), and Spyware Blaster (anti-spam for IE).
I am also running a few FireFox anti-spam extension too; Adblock Plus (ad sites frequently have spam scripts), Adblock Filterset.G Updater (works with Adblock Plus), NoScript (blocks all java/flash/plugin scripts unless you allow a site), and lastly SiteAdvisor (new beta software than works with Google/Yahoo to warn you if your search results point to websites that spam and/or run scripts/downloads--you may have issue that it reports search results back to server).
Running IE and Outlook are just invitations for disaster.
-Bill