Microsoft Security Essentials it calls itself. Came free via Microsoft update. So I ran it in "full scan mode" overnight. It reported that it checked 1.8 million things on my hard drive and found seven "threats", all with the name of Java something-or-other. Upon command it zapped all seven "threats". It didn't call out tracking cookies as hostile which is nice and keeps blood pressure low among us users.
My PC survived the experience, so here we have a nice free antivirus scanner.