Search Bar On Megaupload Does Anyone Know How To Make Google The Search Provider For Firefox?

Does anyone know how to make Google the search provider for firefox? - search bar on megaupload

I have recently installed megaupload toolbar, and since then things if you're in the address bar of Mozilla, I get redirected to a Yahoo search. Before, if I wrote something like Wikipedia, then I go to Wikipedia. I uninstalled the Megaupload Toolbar, but every time I write, what in the address bar, I am still at a search site Yahoo. All ideas on how to get rid of them and bring them back normal? Thank you in advance.