Consider yourself Lucky!
Autocad 2012 is a downgrade from 2011, big time!
They don’t talk about it’s new features for a reason, and the reason is that THERE ARE NONE!
They changed the UI once again to have a smaller workspace and be cluttered with 3D crap.
What where they doing all year?
While you wait here for an answer to your question. I would recommend you also ask your question in the Installation & Licensing forum which can be found at the following link.
For more information on this known Autodesk Support Knowledge Base article, please follow this link:
Thank you ,i finnally succeeded with your autodesk help,i deleted the "broken zone" above "0-4 zones"'restarted my computer and all works .