Sidebar display Category with Parent and Child – help

I’m not sure how to do this and I have spent two days trying to figure it out.
What I’m trying to do is, list a single category in the sidebar and have it display the children indented below.

*Parent Category
**Child Category
***Child2
**Child Category
***Child2

I have been able to display the parents but not the child…
Here is the code I have so far… I’m sure it is all jacked-up and missing a lot because I don’t know much about php…

<ul>
<?php wp_list_categories('hide_empty=0&hierarchical=1&title_li=&exclude=4,1,5,'); ?>
<?php while (have_posts()) : the_post(); ?>
<?php endwhile; ?>
</ul>

Any help you can provide is much appreciated. 🙂