Your system details list shows a Bing Search extension , so you can uninstall that extension.

• https://support.mozilla.org/kb/Uninstalling+add-ons
• https://support.mozilla.org/kb/uninstalling-toolbars

See also:

• https://support.mozilla.org/kb/remove-toolbar-has-taken-over-your-firefox-search-

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

If you need to reset search related preferences then look at the SearchReset extension:

• 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).

Thank you very much, but it's not the Bing Toolbar I want to remove. mysearchresults.com seems to be the search engine the bar leads to.

The extension seems to hide under a name that starts with Default and you have the Default Tab extension, so remove that one.

• [/questions/927599]
• [/questions/941822]

See:

• https://support.mozilla.org/kb/remove-toolbar-has-taken-over-your-firefox-search-

Try to reset the prefs on the about:config page that refer to mysearchresults.

• Open the about:config page via the location bar and do a search for mysearchresults via the Search bar at the top of the about:config page.
  
• Reset all mysearchresults related prefs that appear bold (user set) via the right-click context menu to their default values.

If you do not keep changes after a restart then see:

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