After the Installation of Xmap, a SEO Sitemap Component for Joomla, it is possible that Joomla don't display Xmap in the components of your Joomla 2.5 Administration. The easiest way to know that is, if Joomla reports after the installation of Xmap following message:

Another Menu item with the same parent has this alias

Error building Admin Menus

The installation of Xmap was indeed successfull, but Xmap will not displayed.

This error occurs, if you try to install Xmap again, after a failed installation. Then, you have two options to solve this error.