Search for the preference: plugin.expose_full_path.
   Double-click on the plugin.expose_full_path preference in the list to change the value to true.
   Enter about:plugins into the Location bar to display the About Plugins page.
   Each entry in the About Plugins page will have "File name:" followed by a path. Use Windows Explorer to navigate to the folder shown for the plugin you want to remove.
   Rename the file to something other than its normal name - e.g. npswf32 becomes Xnpswf32
   Double-click on the plugin.expose_full_path preference in the list on the about:config page to change the value back to false to avoid exposing the plugin path to websites. 

i read an answer about manually uninstalling plugins from the add-on menu, this is what was suggested - In the Location bar, type about:config and press Enter. The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!, to continue to the about:config page. Search for the preference: plugin.expose_full_path. Double-click on the plugin.expose_full_path preference in the list to change the value to true. Enter about:plugins into the Location bar to display the About Plugins page. Each entry in the About Plugins page will have "File name:" followed by a path. Use Windows Explorer to navigate to the folder shown for the plugin you want to remove. Rename the file to something other than its normal name - e.g. npswf32 becomes Xnpswf32 Double-click on the plugin.expose_full_path preference in the list on the about:config page to change the value back to false to avoid exposing the plugin path to websites. The plugin will be removed. I searched for plugin.expose_full_path which i cannot find, is their any easier way to remove plugins i don't need?