If you've got a hardware firewall, and most routers come with hardware firewalls, a software firewall isn't really needed. But many, including myself, use the windows built in firewall; [winkey]+[R] > firewall.cpl
Failing that comodo is free and has been recommended by several members here.
Comodo also do a free av package. Some members use the free versions of AVG or Avast.
Don't forget about spyware and adware. These can be sorted by Spybot Search and Destroy, Ad-Aware and/or hijackthis.