Can't get rid of adware--no program will remove it.

Since about July or August, I've had this really stupid adware infection. I don't know how I got it, but it's a click-redirect adware and everytime I click a link on a search engine, I'll be redirected to some stupid ad site and have to hit the back button and click again to get to the link. I have Malwarebytes, Spybot Search and Destroy, and Norton Antivirus and have run scans on all three of them multiple times since then. It won't remove it. I don't know how to remove it manually because I don't know what it is that's causing it. How do I get rid of this?