Adding an identity to an existing column

http://blogs.msdn.com/b/dfurman/archive/2010/04/20/adding-the-identity-property-to-a-column-of-an-existing-table.aspx
http://blog.sqlauthority.com/2009/05/03/sql-server-add-or-remove-identity-property-on-column/

I think we can't alter the Column for identity.
so the possible solution is:- 

        a).        Either Create a new table with Same Fields and Structure and apply identity to the column at that time and then drop the previous table.

        b).        Create a new Column with same Datatype and Apply Identity to it and then delete the Column(previous).