Joomla! 1.5 does not provide an upgrade path from earlier versions. Converting an older site to a Joomla! 1.5 site requires creation of a new empty site using Joomla! 1.5 and then populating the new site with the content from the old site. This migration of content is not a one-to-one process and involves conversions and modifications to the content dump.
There are two ways to perform the migration:
In Joomla! 1.5 all User interfaces can be localised. This includes the installation, the Back-end Control Panel and the Front-end Site.
The core release of Joomla! 1.5 is shipped with multiple language choices in the installation but, other than English (the default), languages for the Site and Administration interfaces need to be added after installation. Links to such language packs exist below.