SQL Server connection

i am trying to connect to the sqlserver, i’m working on windows2000, i created a dsn and i’ve chosen SQL server authentication,
now when i try to connect to the SQLServer im receiving this error,

[Microsoft][ODBC SQL Server Driver][SQL Server]Login failed for user ‘(null)’. Reason: Not associated with a trusted SQL Server connection

please help me as soon as possible,

thanks,
charan