If a sub-folder XML file contains an “install” element, the Joomla installer might bypass the intended install xml file for the sub-folder variation. Only the top level installer xml file should have an “install” element. The core Joomla 1.5 Contact component has an administrator file (contact.xml) which contains the “install” element. I used the Contact componenent as the basis of a new component. The installation failed because the installer read the administrator/contact.xml as the installer xml file. The solution was to remove the <install> and all header elements, and to add a top level <config> element instead.
If your installation has this error, you might get this misleading message: “The XML file did not contain an administration element.” This is because the installer is not looking at the correct installation xml file. It’s not that the installation xml file doesn’t have an <administration> element, it’s that the sub-folder installation xml file is overriding the real installation XML file, and the sub-folder XML file does not have an administrator element.
Keep administrator and install in the top level XML file. Don’t use administrator or install in sub-folder configuration XML files.