This is how to remove a CCK-field with a special condition. If you just want to hide the field in hull node and/or teaser view you can configure it at Manage fields / Display fields at your content type.
Don't forget to refresh your them registry before testing, otherwise you wont see any difference. If you are using the admin menu module ( http://drupal.org/project/admin_menu) you find it in the first menu, Flush all cashes /Theme registry.
Create a file, content-field.tpl.php, in your theme folder.
Add the following content to this file: