Errods 0 Newbie Poster

Can you give me some ideas on how to achive the following.......

i myself want to validate the user before he will login to windows............ Like my own login screen insted of winlogin........

Hence I want to overwrite the windows login............... How do i do this?????????

And if the USER Name and Password enterd by the user are correct i want hin to enable using the system by loading the desktop..........

So how can i do this...........