I am a new user of ACA 2013. i HAVE JUST STARTED A TUTORIAL, "... NO EXPERIENCE REQUIRED".
YESTERDAY I LOST THE COMMAND LINE, THE TABS AND THE RIBBON.
HOW CAN I GET THEM BACK.
The easiest way to restore ACA is from Windows start menu, under All Programs->Autodesk->Version Folder, select Reset Settings to Default. Warning, any customization you did will be lost.
For the future please start a new thread with your issue, instead of piggybacking on old threads.