No matter how much anti-spyware protection you've got on your PC, it's not enough. Spyware is notorious for being able to slip through the cracks of anti-malware software, and you're best off if you have more than one anti-malware tool on your PC. That's where this freebie comes in. Use it as a backup to your main anti-spyware program for extra protection.
It doesn't offer "live" protection like some other programs. Instead, use it to examine your system, to see if it's been infected, then kill the malware. It's a surprisingly powerful tool, and with far more features than we can cover here.
But here are the basics: Run it and click the Online Analysis button, and it will check your system for malware, and issue a report online. If it finds any nasties, it will tell you. If the program finds malware, it can walk you through removing it.
There's plenty more here as well, including tools for viewing what programs are using your TCP ports, and examining programs that run on startup. For a free program, it's surprisingly powerful.
Note: The vendor states that this software's functionality is limited on 64-bit systems.