This is by far the best suggestion for you, in my opinion. Both are utilities that track down and remove spyware on you computer that was installed by some site you visited (you probably thought you were getting something for free)
Adaware is here
and Spybot Search and Destroy is here.
Thanks for posting the links, I was too lazy to look them up ^
I should also recommend that once you download the free programs to your computer, you'll have to launch the utility by clicking on the icon on your desktop, then start each program. There are ways to automatically run these utilities on your computer but the first time you'll have to click on the program icon on your desktop once the program is installed.