IE Defender is hijacking my computer, and nothing i have done will get rid of it. Anyone have this experience?

I tried to delete the program, but it is not listed on the menu for uninstall. the anti-spy yahoo has does not get rid of it either. mcafee that is always running tells me there is no problem. i am getting tired of looking at when i use my search engines. has anyone successfully rid their computer of this rotten bug? any help would be mucho appreciado. thanks.