I'm assuming since you posted in the Snow Leopard forums, that's the OS you're using. In which case, AdwareMedic can't help you since it requires Lion as the minimum OS to operate.
You may find the correct manual instructions in the page D.Cohen linked to, but Apple's instructions are usually well out of date. You can find much more up-to-date instructions on The Safe Mac's adware removal page. The only problem there is that it lists the manual removal instructions for all known adware, and you have to figure out which one (or more) you have.
Download and run EtreCheck. Paste the results here. That will allow other users to see what processes are running. Then we'll be able to see exactly what adware is installed.