DavidR
17
Whilst the windows XP firewall is usually good at keeping your ports stealthed (hidden) it provides no outbound protection and you should consider a third party firewall.
Any malware that manages to get past your defences will have free reign to connect to the internet to either download more of the same, pass your personal data (sensitive or otherwise, user names, passwords, keylogger retrieved data, etc.) or open a backdoor to your computer, so outbound protection is essential.
- Zone Alarm free http://www.zonelabs.com works fine with avast (however it is now becoming very bloated with trial software and some are experiencing issues with it) and has a reasonably friendly user interface.
There are others, Comodo gets very favourable comments in the forums.
See some firewall tests for comparison, some are freeware but many are paid for versions http://www.firewallleaktester.com/tests.php. Also see http://www.thefreecountry.com/security/firewalls.shtml