Maintaing Folder Structure

I have multiple project folders on a networked drive being accessed by
multiple users. They are stored on a Server 2003 machine, each user had XP
pro and belongs to company domain.
How can the folders be setup so that users can access, create, edit files
inside each project folder, but can't accidentally delete or move an entire
project folder.
I tried changing project and subfolder security settings, but while project
folder remains, all subfolders still get moved.
Any help or suggestion is much appreciated.