Joomla 1.5 has it's own build in search engine friendly (SEF) component that is relatively easy to turn on.  It is best to try using this first before installing another component or module to do the same thing.  I've used Joomla SEF very successfully and it is so simple to turn on.

Firstly you need to go to your File Manager in your CPanel, or ftp program to find a file called "htaccess.txt" that comes as a default file after the installation of Joomla 1.5.  All you need to do is either, click on the name and rename it, or click on edit name and rename this file to .htaccess and then we are ready to prepare Joomla SEF.

Once you are back in the Joomla control panel, click on "Site" then "Global Configuration" and you will see on the right hand side the Joomla SEO Setting parameters which are automatically all set to "no".   Click them all to "yes" and that's all there is to it.  Joomla SEF is now set up.

There are some things to note however, Joomla SEF works through the menu's so if you change your menu's around, attaching, reattaching and swapping between menu's then this will muck up your Joomla SEF settings and your visitors, if they come across your site through the search engines may end up clicking on a dead link because you have moved things around.  Just be aware of this.