How get 1 back to ID column?

Now, I have a table, tTest at a MS SQL server database. Only 2 columns for it, ID and Name. ID is the primary key, and its seed is 1 and will  automatically increase by 1 when a new record is inserted. The test data is: 

ID  Name

1    A

2    B

3    C

After deleting all rows, I would like to insert another row "1  X". But I can only get "4  X". How to get "1  X"? Thanks a lot