EWF

The following paragraph i quote from an online article

Differences Between Windows XP Embedded and Windows XP Professional

by Katherine Enos
Microsoft Corporation
December 2004
Applies to Microsoft® Windows® XP Embedded
...
Embedded device disk volumes often require protection against improper disk write operations. Windows XP Embedded provides Enhanced Write Filter (EWF) as a solution for this scenario. EWF protects the contents of disk volumes by redirecting write operations to a different storage location, which is called an overlay. This strategy allows write operations to be made without affecting the original contents of a disk volume. Configuration information about the EWF-protected volumes on a device is stored in unpartitioned disk space on the same disk. You can use EWF on devices that start from a bootable CD-ROM because EWF allows read-only media, including CD-ROM and flash, to boot and run.

Ok, several of the articles i have run into have stated that
you must include EWF support to your target image to boot from a cd.