OS Deployment covers this kind of scenarios leveraging on Scripting Toolkit Windows Edition (based on Windows PE) provided by the main hardware vendors like IBM, Dell, HP. You can create your own
custom hardware configuration installing on a dedicated machine the Scripting Toolkit suitable for your HW and then create a customized bootable Windows Preinstallation Environment (Windows PE).
The .rad file is the way OS Deployment packages the Scripting Toolkit to allow to be imported and then deployed on the targets that completed a PXE-boot. The target will load the Windows PE and then starts the execution of the hardware configuration as your prepared with Scripting Toolkit.