Get Spybot: Search and Destroy
[link|http://www.safer-networking.org/|http://www.safer-networking.org/]
Beware that Kazaa has Spyware installed and if you remove it, it will no longer work. You may want to try Kazaa Lite instead, even if it is a hack of Kazaa, because it lacks Spyware.
I told my college instuctor about it when his system was doing the same thing, and someone stole his password to send out Spam. He ran Spybot and found over 500+ Spyware/Adware programs on his system. Many of them keyloggers, etc. System ran 1000% better after he removed the Spyware/Adware.