I was trying to manually restore some files from a previous installation of Firefox, and in so doing I messed something up and now one of my addons is not working properly. I tried removing the addon by clicking the Remove button next to it in the Extensions section of the Addons Manager, restarting, reinstalling the addon and then restarting again, but it still does not work properly. It appears that the only way to fix this is to completely uninstall and wipe Firefox and all associated files and reinstall it again, and then reinstall the troublesome addon and any others I might wish to keep. How can I do this?