The NDIS layer of Windows CE 5 loads the driver IPNAT.DLL. This DLL is responsible for the Network Address Translation and for the DHCP allocator. Unfortunately NDIS loads the driver by its name without any visible entry the registry. That's why your device just lakcs the NAT functionality when you create a platform without the DLL.
I need to change the configuration of my device.
How can I inhibit the load of the IPNAT.DLL without rebuilding with the Platform Builder?
Windows CE loads always the DLL with the name IPNAT.DLL. As long as the file is in the flash ROM it's impossible to inhibit loading if that DLL.