There is a new option added in SQL Server 2008 for modifying tables while using the Table Designed in Management Studio which will prevent saving any changes to a table that needs a drop/re-create of the table. The error that you would see in the Management Studio is:
TITLE: Microsoft SQL Server Management Studio
User canceled out of save dialog
(MS Visual Database Tools)
If you want to modify a table property through the UI which requires a table recreation, then you need to change the following options in Management Studio:
Tools ->Options-> Designers -> Table and Database Designers -> uncheck the option "Prevent saving changes that require table re-creation"