Convert computed column to regular column

-- Create a new Column (unpersisted):
ALTER TABLE MyTable
   ADD newColumn DatatypeOfPersistedColumn
GO

UPDATE myTable
SET newColumn = PersistedColumn
GO

-- Delete the persisted column
ALTER TABLE MyTable
   DROP COLUMN PersistedColumn
GO

-- Rename new column to old name
EXEC sp_rename 'MyTable.newColumn', 'PersistedColumn', 'COLUMN'
GO

The poster wants to keep the name of the column. I have added a line at the end of Mitch's code to do a rename after dropping the PersistedColumn

-- Create a new Column (unpersisted):
ALTER TABLE MyTable
   ADD newColumn DatatypeOfPersistedColumn

UPDATE myTable
SET newColumn = PersistedColumn

-- Delete the persisted column
ALTER TABLE MyTable
   DROP COLUMN PersistedColumn

-- Rename the new column to the old name
EXEC sp_rename 'MyTable.newColumn', 'PersistedColumn', 'COLUMN'