If you computer is being infected with worms and viruses constantly then consider installing the kerio personal firewall which is absolutely free for personal use.
The installation and configuration are pretty easy. Setting up firewall rules is a breeze. I definitely recommend this for every one who has windows 2000 or XP> You should disable Windows XP's builtin firewall before you begin installing this.
the only glitch I found was that if too many programs are accessing the net then the configuration dialog takes a little time to popup.