How can I uninstall the Google toolbar on Mozilla?

I don't want Google as my dafualt search engine in the box on the top right. I want it to be Wikipedia, but I can't seem to do that. And everytime I do its gone the next day. And i try uninstalling Google toolbar but I couldn't find it under the list of Add/Remove hardware|||go to the link below,that is the instructions to remove the toolbar|||click the show update's in add remove once you have it open and rescan, it should show up now. if not click tool's atop the web browser and click manage plugin's and remove it that way.