To show only main cats, replace in includes/functions.php $drop_down_cat_cache = $cat_parent_cache;
with: $drop_down_cat_cache[0] = $cat_parent_cache[0];
And to sort them by name, below that line, insert: uasort($drop_down_cat_cache[0], "catsortname");
then, at the very end of the file, ABOVE closing ?> insert:function catsortname($a, $b)
{
global $cat_cache;
return strcasecmp($cat_cache[$a]['cat_name'], $cat_cache[$b]['cat_name']);
}