http://www.malwarebytes.org/

But I still like SpyBot as my first choice.

What I don't understand is how AntiVirus200X keeps getting past all of the security software installed and then avoides detection by the same "high-end" software.

I've seen Windows Happily install AntiVirus2009 on a machine running an up to date client of OfficeScan. And then had to install AntiMalware to get rid of the dam thing.