AVG is excellent software; free, too! But you should update the virus definitions database at least once a week.
IMHO, a firewall that protects against just inbound threats, such as that built into Win XP SP2, is worthless as it does not protect against unwanted outbound traffic such as keyloggers calling home.
FWIW, I use the free(!) Kerio firewall. Excellent!
Thank you! I will try Kerio at once.