McAfee AntiVirus Plus 2010 (1-User) for $10.99 shipped.  Here is a screenshot for your reference.  This program shields PCs from viruses, spyware, and has a firewall to protect against network attacks.  It also features McAfee SiteAdvisor that warns about risky web sites before users visit them.  Note that the 3-user license version is available here for $18.99 with free shipping on orders over $25.