Don't worry, Mac viruses are coming as soon as they get a bigger market share. They are not worth the effort for most loser hackers right now.
To clean your PC for the average user (all freeware):
- SpyBot Search and Destroy (be sure to Immunize too to prevent further incidents)
- Ad-Aware (it removes annoying data miners and little else)
- CWS Shredder (removes all variants of the Cool Web Search spyware)
Hijack This is great, but not for the average user.
As for Virus Scanners, they do not effectively block spyware. It is recommended to change virus scanners every year or two. Once a scanner becomes effective and/or popular it becomes a target for virus writers. The new AVG is riddled with its own spyware, so avoid it. NOD32 is no longer effective, and it was great for years. Norton, McAffee and that shit is exactly that, shit, because it too is riddled with spyware and wants to eat all of your system resources. The new Avast is pretty good, as is PC-cillin. Bit Defender kicks ass, but is SLOOOOOOW, and a resource hog.
Never use anything that says "Internet Security" or anything like that. If it says that it means that it will try to control everything coming in or out of your machine, and that gets a little tired. If you immunize with Spybot, and do frequent scans (weekly) you should be okay. I used to make $70/hour off of people who trusted Norton/McAffee or went without scanners. Trust me, the money was very good.