How can I alter this computed column in SQL Server 2008?

Something like this:

ALTER TABLE dbo.MyTable
DROP COLUMN OldComputedColumn

ALTER TABLE dbo.MyTable
ADD OldComputedColumn AS OtherColumn + 10

Source

If you're trying to change an existing column, you can't use ADD. Instead, try this:

alter table tbPedidos alter column restricoes as (cast(case when restricaoLicenca = 1 or restricaoLote = 1 or restricaoValor = 1 then 1 else 0 end as bit))

EDIT: The above is incorrect. When altering a computed column the only thing you can do is drop it and re-add it.

This is one of those situations where it can be easier and faster to just use the diagram feature of SQL Server Management Studio.

1. Create a new diagram, add your table, and choose to show the formula column in the diagram's table view.
2. Change the columns formula to an empty string ('') or something equally innocuous (probably such that you don't change the column's datatype).
3. Save the diagram (which should save the table).
4. Alter your function.
5. Put the function back in the formula for that column.
6. Save once again.

Doing it this way in SSMS will retain the ordering of the columns in your table, which a simple drop...add will not guarantee. This may be important to some.