How to Resent identity values when one of the record is deleted ?

Hi,

I had set a identity to column (s.no) of Table and inserted values into a table . when some of  records are deleted 

Here serial number 1003,1004 is missing in this table . so, i want to reset identity column to an order (i.e 1001,1002,1003,1004,1005) .

please solve this problem