Hello There,
I've had same problem that you are discribing. I kept getting the An error is preventing Windows from accurately checking your license message (or something along those lines).
And I at some point I noticed that the machine I was building my XPe image for was a Multiprocessor PC. So I checked my target designer config and saw that only the advanced confiuration power interface (ACPI) PC was added. I got rid of that error by deleting the Advanced configuration power interface (ACPI) PC component and adding the Multiprocessor PC component.
I hope this solves your problem.
Dennis van Gurp