Could you post a screenshot of your screen?

What is the name of that extension? Extensions that do not have a "Remove" button are installed globally by other software and are not under control of the Firefox extension manager. Globally installed extensions are usually found via a registry scan or are installed in a location that Firefox scans for installed extensions. *https://developer.mozilla.org/Installing_extensions *https://developer.mozilla.org/Adding_Extensions_using_the_Windows_Registry Extensions installed globally need to be removed via the settings (Options/Preferences) of the program that has added this extension or this program has to be uninstalled via "Control Panel > Programs". In Firefox you can only disable such an extension. You can check the install location in the extensions.json file in the profile folder. You can open the extensions.json file in the Scratchpad and search for this extension. The descriptor field should list its install location. *https://developer.mozilla.org/Tools/Scratchpad You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page. *Help -> Troubleshooting Information -> Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox