newbie: how convert nvchar to datetime?



I have imported a table into msSQL (2000)
One of the fields which was stored originally as a simple date field (05/05/05) was created as nvarchar(8).


How to I alter this column to become a DateTime field type?
I want to do this before I add any more records.

The application will be sending a date like 10/23/2005 but without the time part.
.