Avast A/V, malwarebytes, ccleaner, spybot s & d. I love the boot time scan from Avast, catches all kinds of nasties, and i find what it doesn't catch, malwarebytes does. I haven't tried M$ Security Essentials yet, but i'm iffy on the idea of an A/V product from a company that specializes in operating sytems - and sometimes misses the mark.