For Windows Xp:
1. ) Go To Start => Run => Type “control userpasswords2” and Enter.
2. ) Now Select the user for which you want windows to login automatically without asking you any password and Uncheck the box “Users must enter a username and password to use this computer”.
3.) Now Click Apply, It will Prompt to Enter Password for that user name. Enter the password and Click Ok.For Windows Vista & Windows 7:
1. ) Go to Start => Type in Search box “netplwiz” and Enter
2.) Now Select user from the list for which you want to login automatically and Uncheck the box “Users must enter a username and password to use this computer”.
3. ) Now Click on Apply, it will Prompt to Enter Password for that username. Enter the Password and Click Ok.Once you are done with the above settings, You will be able to login to Windows Automatically without entering any password.