With Netscape Communicator, click the Help menu, then click About Plug-ins. With Netscape Navigator, type about:plugins into the Location field and press Enter. You will see information on all the plug-ins that are installed in that copy of Netscape software. For instance, if you have the Real Player plug-in installed, it will look something like the following. You only have to be concerned with the bold heading. If you see the plug-in listed, then it is installed.

Under the Enabled column, it will sometimes say No. This means that the plug-in is disabled for that particular file type, because another installed plug-in is handling that file type. There is no way of specifying which plug-ins should handle which file types.