This is possible:
You will need to edit includes/categories.php and look for the line that is:
Code:
$categories_data = func_query("select $sql_tbl[categories].*, 0 as product_count from $sql_tbl[categories] ".($current_area=="C"?"where $sql_tbl[categories].avail='Y' $membership_condition ":"")." group by $sql_tbl[categories].categoryid order by ".($current_area=="C" ? "order_by" : "category"));
to be:
Code:
$categories_data = func_query("select $sql_tbl[categories].*, 0 as product_count from $sql_tbl[categories] ".($current_area=="C"?"where $sql_tbl[categories].avail='Y' $membership_condition ":"")." group by $sql_tbl[categories].categoryid order by ".($current_area=="C" ? "category" : "category"));
This will effectively disable the order by column and make it order by category name.