[support] FILE SYSTEM: PRIVATE vs PUBLIC

Ok I am confused about PRIVATE and PUBLIC set for the FILE SYSTEM

I am taking a site and copying it to the same root area with a different name so I ended up with drupal 1 and drupal2. I also created a different temp directories, just to be safe. Drupal1 is the original and the FILE SYSTEM is set up to PUBLIC and everything works.

On drupal2, If the FILE SYSTEM is set to PUBLIC then my ddblock module will not display pictures and I get an error message "The selected file 'D:\temp\filAB2.tmp could not be copied."

But if I set drupal2 FILE SYSTEM to PRIVATE then everything works.

Can some help understand why I can not set both the original and the copied site exactly the same?

Thanks,

Nestor