ok - I finally got my download links to work correctly.
The files (zip files) to download are in a 'secure' folder off of the site root.
The link is in the format :
http: // www.web_site_name.com / store_virtual_dir_name /LinkClick.aspx?fileticket=56dtWsm6vs%fa
The links work well.
The link still works well even after you sign out!
There is no security, just replacement of the actual path to the file name.
How am I able to secure the file???