Joomla! Documentation™

Some Joomla 2.5.x core components (Banners, Contacts, Newsfeeds, Smart Search, and Weblinks) can be deleted via the Back-end: Extensions > Extension Manager > Manage > (select + delete)

Core component installation packages don't exist because it's too much work to maintain, and Joomla 2.5 has a nice feature called "discover".

Note: The following method is recommended:

1. Upload and merge the contents of a Joomla full package (without /installation/ directory) to the root of your website. If you're comfortable with SSH you can unzip the package and merge it. Otherwise, use an FTP client that lets you do a merge/replace and choose merge for any folder your ftp client asks you about and overwrite for any file it asks you about. Using merge for folders instead of just replace will leave your non Joomla files alone (things not included in the install package) while replacing only the files that are in the package you're uploading with new ones and replacing any missing files. WARNING! if you simply upload and don't merge, you'll overwrite anything installed and likely break your site.
2. Use Extensions > Extension Manager > Discover to discover & install uninstalled extensions.
3. The components table structures + the component reference in #__extensions + the component menu items will all be created automatically.
4. The component reference in #__assets will not be created using "discover": to recreate, use Components > [component name] > [Options] (icon in upper right corner) > Permissions (tab) > [save & close]

If you're doing this to repair a broken upgrade, you'll also want to use the database repair function found in the extensions manager area to fix the database.