Ad-Aware and Spybot S&D
I have been using these two free anti-spyware tools for at least three years now. As btljooz mentioned they do compliment each other perfectly.
They are both regularly mentioned and highly rated by various PC magazines and are completely safe to use. I have never had any problems uninstalling them.
Obviously, as with any programs, make sure you download the installers from the manufacturers site or reliable source. I always d/l Ad-Aware from Lavasoft directly.
I also use Kaspersky Anti-Virus, I find it's a lot more efficient and unobtrusive than Symantec or McAfee products. It will list some Ad-Aware files after a scan, but only to say they were password protected and it was unable to scan them. Don't confuse this with a possitive virus detection, the files are perfectly safe.
