How to solve "Saving changes is not permitted. The changes that you have made require the following tables to be dropped and re-created."

Disable “Prevent saving changes that require the table re-creation” 

1.    Open SQL Server 2008 Management Studio (SSMS). Click Tools menu and then click on Options… as shown in the snippet below.

2.    In the navigation pane of the Options window, expand Designers node and select Table and Database Designers option as shown in the below snippet. Under Table Options you need to uncheck “Prevent saving changes that require the table re-creation” option and click OK to save changes.

http://www.sql-server-performance.com/2009/saving-changes-not-permitted/