will the column support NULLS? if it can, you could update the data to be null where the column is that value.
it really depends on the table and the columns' datatype .
also, will your application crash if it gets a null value for that field, assuming it's trying to populate a datepicker control or something?
UPDATE YOURTABLE
SET ThatColumn = NULL
WHERE ThatColumn = '1900-01-01 00:00:00.000'
Lowell