Kim Komando has a website with all these programs listed as freeware, and she recommends AVG for viruses, and Spybot for spyware. Look for Komando.com.
I run AVG AntiVirus. I also use in this order: Spybot Search & Destroy, then AdAware. It sometimes takes both spyware programs to catch everything, although lately this has become less of a problem, with Spybot doing a better job of updates.
I don’t think I would ever trust a single program to find all the spyware, since some of those programs leave their own traces.
Hey! I thought SpyBot is free. I downloaded it and then to sweep my computer I have to pay 20 bucks.