Varchar(255) to Varchar(MAX)

You should be able to do it using TSQL.

Something like

ALTER TABLE [table] ALTER COLUMN [column] VARCHAR(MAX)

'Saving changes is not permitted. The changes 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 table to be re-created.' Option 'Prevent saving changes' is not enabled..

That's a new "feature" in SQL Server Management Studio 2008 which by default is turned on. Whenever you make a larger change, SSMS can only recreate the table by creating a new one and then moving over the data from the old one - all in the background (those changes include re-ordering of your columns amongst other things).

This option is turned off by default, since if your table has FK constraints and stuff, this way of re-doing the table might fail. But you can definitely turn that feature on!

It's under Tools > Options and once you uncheck that option you can do these kind of changes to table structure in the table designer again.