Open includes/functions.php and change
$user_name = $image_row[$user_table_fields['user_name']];
$user_profile_link = (!empty($url_show_profile)) ? preg_replace("/{user_id}/", $image_row['user_id'], $url_show_profile) : ROOT_PATH."member.php?action=showprofile&".URL_USER_ID."=".$image_row['user_id'];
$user_name_link = "<a href=\"".$site_sess->url($user_profile_link)."\">".$user_name."</a>";
to
$user_name = $image_row[$user_table_fields['user_name']];
if ($user_name == '<admin_username>') {
$user_name = '';
$user_name_link = '';
} else {
$user_profile_link = (!empty($url_show_profile)) ? preg_replace("/{user_id}/", $image_row['user_id'], $url_show_profile) : ROOT_PATH."member.php?action=showprofile&".URL_USER_ID."=".$image_row['user_id'];
$user_name_link = "<a href=\"".$site_sess->url($user_profile_link)."\">".$user_name."</a>";
}
Replace <admin_username> with username of the administrator
Jan