The function tep_get_category_tree is the one that creates the contents of the drop-down menu (the one that starts with Top) in the top right corner of the categories.php page in the admin section. In the 2.2MS2 version of osCommerce it is very inefficient as relating to mySQL queries. It queries the database for every category, subcategory, or subsubcategory. If you have a lot of categories it will make that page load slow.