In this article you will find all the necessary steps to perform to translate a old joomla 1.0 template into the new 1.5 CMS version.

First of all look into the index.php file for the following occurrences and replace them according to the schema here below:

_VALID_MOS with _JEXEC

$mosConfig_absolute_path with $this->baseurl

$mosConfig_live_site with $mainframe->getCfg( 'live_site' )

use the expressione JText::_( 'stringa' ) for fixed strings

mosGetParam calls with JRequest::getVar calls 
  $id = mosGetParam( $_REQUEST, 'id', 0 ); => $id = JRequest::getVar( 'id', 0 );

mosShowHead(); with <jdoc:include type="head" />

mosMainBody() with <jdoc:include type="component" />

mosLoadModules( $position_name, $style ); with <jdoc:include 
type="modules" name=$position_name style=$style />

if(mosCountModules('position_name')) with if ($this->countModules('position_name'))

Another step is to define block module positions: in the new 1.5 joomla version this operation has to be performed by the xml description file included in the template directory.

<positions>
  <position>top</position>
  <position>left</position>
</positions>

Don't forget finally to modify the xml template header as per the 1.5 joomla terminology:

<install version="1.5" type="template">
has to replace the old

<mosinstall type="template">
joomla 1.0.x statement

A templateDetails.xml file could be also created and added to the template directory installation to store the template parameters.