ESET Rogue Applications Remover is a simple tool which aims to do just what its name suggests: find and remove rogue antivirus programs and similar malware which your regular security tool might have missed.
The program doesn't require installation, and doesn't provide any real-time protection: it's just about running on-demand scans of your PC. It's a little on the basic side, then, but this does at least mean there's very little chance of Rogue Applications Remover conflicting with other security tools - whatever else you're running, you shouldn't have any problems.
To give the program a try, just run it (as an administrator on Vista, or later: right-click, select Run As Administrator). It's a console application so a command line window will open, and you'll see various messages as the program alerts you to its progress. And if Rogue Applications Remover detects any dangers then it'll try to close the malicious processes down, and delete their files.
(Need more control? The program has a few command-line switches, too - the ESET site has more details.)
Does this work? We saw one or two false posirives, so perhaps you shouldn't take Rogue Applications Remover's verdict for granted, but don't let that put you off entirely. It's super-small at under 3MB, easy to use, and is worth keeping around for emergency usage.