Spyware Blaster
http://www.javacoolsoftware.com/spywareblaster.html
is always the first thing I install on a machine. It disables the bad guys and prevents new ones from being installed.
If you have kids, they will not see the invitations to install spyware.
While reading this thread, I remembered I had Spyware Blaster and looked at it again- I have downloaded the most recent version and it's so easy. Don't have to turn it on ever..it just works!