In this article we will try to give a detailed step-by-step guide of how to upgrade one Joomla! 1.5 site to a newer version.
SP Upgrade can be used for upgrading Joomla! version 1.5 sites. For upgrading from version 1.0 to 1.5, use this guide: https://forum.joomla.org/viewtopic.php?f=36&p=3331274#p3331274