Try this: Click your Search button. When the left pane shows, grap the divider and expand it until you see the Customize button. There are some options there to set the search engine(s) you do want.
As far as getting rid of it altogether, someone else might be able to help you with that.
Somehow I ended up with a Yahoo search engine/toolbar, which comes up everytime I try to do a search. I dont like it I dont want it, but cannot figure how to get rid of it. The uninstall option will not work.