<p>In SQL Server 2000/2005,</p>

<p>Is it possible to force the default value to be written to already existing rows when adding a new column to a table <strong>without</strong> using NOT NULL on the new column?</p>

I doubt it.
http://msdn.microsoft.com/en-us/library/ms190273(SQL.90).aspx
The approach recommended by Microsoft is as follows (taken from the url above)
```
```
UPDATE MyTable SET NullCol = N'some_value' WHERE NullCol IS NULL
ALTER TABLE MyTable ALTER COLUMN NullCOl NVARCHAR(20) NOT NULL
```
```