If you're on cable/dsl with a router that has a firewall, why do you need a firewall on your computer?
If you just use the computer for email and a little web surfing then the router along with the Windows Firewall is usually good enough as long as you have a little common sense. But most people aren't much smarter than a bag of hammers which can get you into trouble. When Aunt Flo sends you an attachment with a malicious program a good firewall will let you know and can block it from phoning home. Lately I have been getting emails directing me to fake banking websites, a worm would be installed through your web browser and a firewall would stop it from downloading further instructions.
You can also pick up a few nasties if you download programs using bittorent. Even if you do get a worm it does no damage if it is blocked by a firewall and can't connect to the internet.
The Windows Firewall in XP, Vista, and 7 does not have good outbound packet filtering. Windows Vista’s built-in Firewall does a decent job of blocking incoming requests. It is capable of blocking outgoing requests as well but that feature is turned off by default. A firewall that doesn't have any control over outgoing traffic is quite dangerous because a malicious program can mass-email spam, forward passwords, credit card details and any other critical information to the wrong person.
Wayne
