An alternative for sp_unbinddefault
As per BOL rather than KB, use ALTER TABLE

ALTER TABLE Mytable DROP &lt;defaultname&gt;;


The name of the default could be user supplied or system generated. To find it and generate the SQL needed:

SELECT
    OBJECT_NAME(c.object_id), dc.name,
    'ALTER TABLE ' + QUOTENAME(OBJECT_NAME(c.object_id)) + ' DROP ' + QUOTENAME(dc.name);
FROM
    sys.columns c
    JOIN
    sys.default_constrainst dc ON c.columnid = dc.parent_column_id AND c.object_id = dc.parent_object_id
WHERE
    c.name = 'UW_ZeroDefault';