look the following
2 User ID is not valid.
5 User ID is not valid.
6 An attempt was made to use a Windows login name with SQL Server Authentication.
7 Login is disabled, and the password is incorrect.
8 The password is incorrect.
9 Password is not valid.
11 Login is valid, but server access failed.
12 Login is valid login, but server access failed.
18 Password must be changed.
MCTS SQL Server2k8