Unhandled exception with user login failed.

I am facing an exception when I run a windows program. The code is about select userid, password in the database. The method calls the stored data for login in database. Bu t I can't able to access data from table because 'An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll Additional information: Login failed for user', when running a program and, also i enabled SQL server and windows authentication mode but again it show that same exception only. I using SQL server authentication in windows application. Please help me.....