How to remove search engines from the Firefox search box (this tip is for Windows users. Others should be able to find similar files in their program directory
* Windows users go to C:\Program Files\Mozilla Firefox\searchplugins
* Mac OS X users go to /Applications/Firefox.app/Contents/MacOS/searchplugins
* Linux users go to /usr/lib/firefox-1.0.1/searchplugins
* Each search engine has two files; a .src and either a .png or a .gif file. All you have to do is delete the two files for the search engine you wish to remove (for example google.src and google.gif) and restart Firefox.