Probably the Best Free Security List in the World- Courtesy of Gizmo's : http://www.techsupportalert.com/content/probably-best-free-security-list-world.htm
spybot (and spywareblaster) are perhaps best because you can "immunize" your system against future problems. things similar to Norton SytemWorks and CCleaner can be good for a system. I had a friend who had a 75Gb hard drive that was totally hammered - 99.9% full and slow as Antarctic granite. Finally, after running the norton stuff 4 times, disk defragmenter, ccleaner and other stuff got it down to 40% full. (took quite a few hours and sleuthing. Told them "ya gotta run your malware apps, antivirus, defragmenter at LEAST once a month and keep them up to date!!!" Some of the stuff hadn't been updated in 12 months...