When you use Data Definition Language (DDL) to modify a table, and then you try to save the table in Microsoft SQL Server 2008, you may receive the following message:

Saving changes is not permitted. The changes that you have made require the following tables to be dropped and re-created. You have either made changes to a table that can’t be re-created or enabled the option Prevent saving changes that require the table to be re-created.

To change the Prevent saving changes that require the table re-creation option, follow these steps:

  1. Open SQL Server Management Studio (SSMS).
  2. On the Tools menu, click Options.
  3. In the navigation pane of the Options window, click Designers.
  4. Select or clear the Prevent saving changes that require the table re-creation check box,  and then click OK.

Source: http://support.microsoft.com/kb/956176