I've been using ZoneLabs free firewall for years: http://www.zonelabs.com/store/content/company/products/znalm/freeDownload.jsp?dc=12bms&ctry=US&lang=en
After you install it, turn off Windows Firewall....I've heard they don't play nice
together.
I have also used Avast Antivirus free version for some time....I like it because
it automatically updates itself and it has worked fine for me, so far.
http://www.avast.com/eng/update_avast_4_vps.html