In Management Studio 2008 a new option is added to prevent save changes that will require a table re-creation. If this option is enabled and you make changes in the table and if that changes requires re-creation of the table, you are not permitted to save changes. To Save changes you need to disable this option.
You can disable this option if you are developing or testing database, otherwise its better to enable this option.
If you want to enable/disable this option Open Sql Server Management Studio, Go to Tools Menu and Click on Options.
A window will appear. Now Go to Designer – > Table and Database Designer. Here you will find the option “Prevent Saving changes that require table re-creation“. You can enable/disable this option.