I have used ZoneAlarm for years and well satisfied... there are others. Go here:
http://www.zonelabs.com/store/content/company/products/trial_zaFamily/trial_zaFamily.jsp?lid=home_freedownloads
Under Special Offers click "Free ZoneAlarm and Trials".
Hope this helps.
Glenn
i,m using avg free anti-virus, does anybody know of a free firewall to go with this please? thanks steve

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic