In SQL 2005 there is no date/time type of data structure that will allow you to store only date part. What people do is to store the date and time with time as 00:00:00.000.
Other methods of storing - for example, storing the date as an interger number of days counted from a well-knownn starting date etc - have been used by some people, but those have their own baggage.
I would recommend using DATETIME or SMALLDATETIME data type, depending on the range.
If your source data is coming in with time portion as well, you can strip of the time portion using the following before stroing it into your table.: