You could customize the sidebox template with your templates and overrides and add the code:
Code:
$content .= '<div id="' . str_replace('_', '-', $box_id . 'Content') . '" class="sideBoxContent">' . "\n";
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";
// $content .= '<br />' . "\n";
$content .= '<hr id="catBoxDivider" />' . "\n";
}
for ($i=0;$i<sizeof($box_categories_array);$i++) {
Then comment out the code in the bottom of the file ...