You can use the SearchReset extension to reset some preferences to the default values.

• https://addons.mozilla.org/firefox/addon/searchreset/

Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).

If you do not keep changes after a restart or otherwise have problems with preferences, see:

• http://kb.mozillazine.org/Preferences_not_saved

Enter “about:config” in url bar. This will open settings page Type “Keyword.url” in the search box. Right click it & reset it. Type “browser.search.defaultengine” in the search box. Right click it & reset it. Type “browser.search.selectedengine” in the search box. Right click it & reset it. Search for ‘browser.newtab.url’. Right-click and reset. This will make sure that the search page won’t launch on each new tab. (via) Make Sure there are no related programs installed in control panel, or the settings might be reverted back.

Hello there, before you start fixing your browser, you need to uninstall Nation Zoom from your computer. One important thing - you need to uninstall not only Nation Zoom browser protection. You should also get rid of these programs that are typically used to distribute Nation Zoom on the Internet: Wsys Control, Extended Protection, eSave Security Control, Desk 365. After that, you should find Nation Zoom's extention and remove it.

Source: my small research and this guide