Windows XP Embedded is a modular version of Windows XP Pro that comes with specific tools to create the OS, and Embedded features that enable scenarios specific to the Embedded area. So the first thing you have to do to build a first Windows XP Embedded is to get the list of peripherals installed on the hardware you are targeting. This can be done using a tool called Target Analyzer. This tool can be run from DOS, Windows or WinPE.
OK, here we are with a virgin hardware (no OS, no DOS, and HD or Flash not even formatted), no floppy disk reader (that could have been useful to boot a DOS from a floppy and run the Target Analyzer tool from there).
Let me suggest a couple of solutions to start working on XPe. Most of the recent hardware (embedded or not embedded) have a BIOS that is compatible with USB boot. That means you can plan to work with a USB Disk on Key to boot "something" in order to prepare and analyze the hardware.
Windows XP Embedded, USB