With the beta release of Joomla 1.5 many people are wondering if the joomla 1.0 templates will work with the new 1.5 version and the answer is yes.

All you need to do is make a change to a configuration setting and your template will work with version 1.5

Before you install the Joomla template theme you need to do the following.

Log into the Joomla 1.5 administrator area.

Choose the Global configuration oprion.

Now select the server tab option

Choose Enable Legacy Mode

Save the settings and now you can install the Joomla 1.0 template

You can find more useful information about this topic at developers blog Templates in Joomla! 1.5 - Part 1