i have found a forum
https://social.technet.microsoft.com/Forums/en-US/f8703055-93b7-4552-b577-ce633f2b52e7/howto-convert-an-evaluation-core-version-to-standard-core?forum=winservercore
with the exact issue im having but havet found and answer that work i have tried everything on the forum but still have no joy