Do I need two firewalls?

I don't know many home computer users who know what a firewall really does and why it's important to know. I'll try to make it simple. There are 2 kinds of firewalls, the software kind (Zone Alarm, the one in XP, Norton...); and the hardware kind (like in your Cable/DSL router). You should have both. The latter protects you from computers trying to connect to you from the outside. The former protects you from that too, plus against rogue programs trying to connect to the outside world. So the hardware one is like a guard facing the world and the software one can pick up the slack and face the computer. While it is important to have 2 firewalls, having 2 software types is not good. Nor is it good to have 2 anti-virus programs running on your PC - they will interfere with each other.

While we're on the topic, are you happy with your anti-virus? Have you been having unexplained software issues since installing Norton or McAfee? Do yourself a favour. Ditch them and go the free route. AVG and Avast are free, don't do more than they need to (why own a Cadillac when all you need is an Aveo?) and are free. Did I mention they're free? I've been using AVG for years now and no complaints.