In Joomla 1.5 you can use so called "overrides" to achieve custom output of components and modules without modifying any core files, which has the risk to get overwritten with the next update.

Basically overrides are just customized versions of the components layouts placed in a folder named "html" located within your templates directory.

Let's take the EventList details as an example:

• Create in your template directory the folder /html/com_eventlist/details
• Copy the file /components/com_eventlist/views/tmpl/default.php in the created directory
• Now this file get loaded instead of the original one.

Now you can customize this file to fit your needs. Keep in mind EventList is in Beta stage und thus in heavy development. We are steadily improving the layouts so we can keep them hopefully untouched when in stable state.

A great Blogpost from Andrew Eddie explains in more detail how overrides work.

Another good resource for in depth information about overrides is the official Joomla documentation about this matter.