I guess that you use the "active update" feature of Norton Antivirus which I've heard is quite good.
The last I heard about Norton's Personal Firewall it was rated as pants, but may have changed. Have a look at Steve Gibson's site (yes, I know he's a bit of a controvertial fellow) - www.grc.com
it tells you everything you need to know about personal firewalls (but were too afraid to ask). Also rates different firewalls - http://grc.com/lt/scoreboard.htm
Alternatively pop down to WH Smith and purchase a copy of PC Pro - great for choosing new hardware/software as they do all the testing for you, and maintain an "A-list" of best-of-class products.