|Win 2k embedded DO exists! I programmed layered drivers for EMC2 for three years in W2k-embedded platform. Wikipedia don't state anything about the no-existence of W2k-embedded, it only says that the predecessor of WES is WinXPe. The hint is in the first paragraph: "Windows Embedded operating systems are available to OEM system builders only, who make it available to end users pre-loaded with the hardware."|
So W2k-embedded is only available to builders like EMC2 or Cisco who distributes it embedded in their carriers.
Answering to the initial question, they are the same thing, but you can't install or reinstall Win-x-embedded by the conventional way, it comes in special storage locations within the HW and with make-ups for the particular HW that make it more efficient than conventional Win.