Your client is a retard. It's not possible to have a file that cannot be deleted. There are ways to fight the user trying to delete it, but you can't make it impossible. You can make it hidden, but you can't stop them from deleting it when they find it. One possible solution, is to store a copy of the file in another location, and when your program runs ( or a service perhaps ), it copies the file back if it was deleted. But, you can't stop users from finding both files and deleting them, either.
Christian Graus - Microsoft MVP - C++ Metal Musings - Rex and my new metal blog "I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )