MS SQL 2012 "Saving Changes is not permitted"

After Create New table and try to add Primary Key later my mssql server 2012 Express not allow me to that but tell me to drop and recreate table instead.

This is bad because long time ago I do this with no problem.
To make it work like before go to
Tools > Options > Designers > Table and Database Designers
and unchecked "Prevent saving changes that require table re-creation" 

Turnoff this option will take the risks.
See more information at http://support.microsoft.com/kb/956176

But I don't need to track my tables because i work on the fly and often set primary key later after create table.