ok lets see if we can step through this

using your favorite editor (I like crimson editor) open both tpl_categories.php and tpl_search.php in includes\templates\YOUR_TEMPLATE\sideboxes. You are using overrides...right. Cause if your not we can't continue,...well we can but it will be under protest.

In tpl_search.php find the following line:
$content .= zen_draw_form('quick_find', zen_href_link(FILENAME_ADVANCED_SEARCH_RESULT, '', 'NONSSL', false), 'get');

copy all from that line to and including:
$content .= "</form>";

Post that code into tpl_categories at the following location:
right after:
if (SHOW_CATEGORIES_BOX_PRODUCTS_ALL == 'true') {
$content .= '<a class="category-links" href="' . zen_href_link(FILENAME_PRODUCTS_ALL) . '">' . CATEGORIES_BOX_HEADING_PRODUCTS_ALL . '</a>' . "\n";
}
}
And before:

$content .= '</div>';

?>

Save the tpl_categories.php and refresh the catalog main page.


Now I know I could have just posted the code and let you copy and paste from here, but would that be fair. We learn by doing and with some guidance we learn better. Actually it was for those that would like to understand the process better.