Firewall or AV? There are good, free ones around. Try one of these, or use Google for more info. Just remember to download from the official sites only
Firewalls ZoneAlarm firewall (click the 'basic ZoneAlarm' button)
Sunbelt Personal Firewall Replaces Kerio & Sygate firewalls. After the free 30 day trial period, the firewall keeps working with basic features only.
Comodo Firewall Pro AV avast! AVG free Avira Antivir