How do I remove the advanced search option from the side box?

This code is in the file indludes/templates/yourtemplate/sideboxes/tpl_search.php

$content .= '<br /><a href="' . zen_href_link(FILENAME_ADVANCED_SEARCH) . '">' . BOX_SEARCH_ADVANCED_SEARCH . '</a>';

This can just be deleted, or commented out.