In fact more that one is better since each catch different things and work in different ways.
SpywareBlaster and SpywareGuard are execellent low resourse software to keep malware off your computer so the others will find less. Just install and occasionally check for reference updates. That's all there is too it and they do their thing. Google for these programs.
I enjoyed recent discussion on this topic & came away with immpression that using all would be best. I was recently looking at "Answers That Work" and they seemed to strongly suggest using only ad aware or spy bot? now
I'm confused again (as usual), has anyone encountered problems using more then one?