> What string conection should I use if I want to run my app from a network drive?

It's impossible. The database always must be on the same physical
machine as the Firebird service, in this case your Embedded DLL.
Firebird does not use database files that reside on a network drive,
be it mapped or not.

If you want to have networking, use the full server (it will also work
on "workstation" OSes like XP).

Regards

Stefan