The pref xpinstall.enabled is only present if it doesn't have the default value true and if that setting is disabled then you would get as far as you were already getting by downloading the file. ---- Delete the files extensions.* (extensions.sqlite, extensions.ini, extensions.cache, extensions.rdf) and compatibility.ini in the Firefox [[Profiles|profile folder]] to reset the extensions registry.<br /> New files will be created when required. See "Corrupt extension files": * http://kb.mozillazine.org/Unable_to_install_themes_or_extensions If you see disabled, not compatible, extensions in "Tools > Add-ons > Extensions" then click the Tools button at the left side of the Search Bar (or click the "Find Updates" button in older Firefox versions) to do a compatibility check or see if there is an update. ---- * http://kb.mozillazine.org/Installing_extensions