You might get a weird error when you try to change a table in SQL Server 2008:

"Saving changes is not permitted. The changes you have made require the following tables to be dropped or 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."

This is followed by a list of tables that can't be changed.

You will probably get this error due to the latter (the option) than the former (the table can't be recreated). To get rid of it, go to Tools > Options > Designers > Table and Database Designers. You should see an option that says "Prevent saving changes that require table re-creation." Uncheck it, and you should be good to go.