The windows firewall and firefox all do it as well put up with vista antiphishing filter is slow as experienced someone hacking through the inconvenience than take the risk actually have lot more trouble with vista hanging for no good reason in web browsers ie netscape and thank goodness dont keep personal or banking.
This is lite on resources and its free.
Avira-(recomended)
free-av.com – Protection and security against viruses, worms, Trojans, dialers more.
*Never install more than one anti virus, as they may conflict with each other.