You may use DBCC CHECKIDENT to reseed (reset) the identity column of any table in SQL Server.
Example:
A table has 10 rows with 10 as last identity. The next record will automatically genrate 11, to start the new identity use the follwing T SQL query in query analyzer.
DBCC CHECKIDENT (tableName, reseed, 15)
To set the seed to zero use the following T SQL query in query analyzer.
DBCC CHECKIDENT (tableName, reseed, 0)
Avoid using a value lower than the current value, doing this will violate the uniqueness contrant in case of new entries.