To change startup color and picture needs you login computer. If can't access pc, you can't do. For password forgotten situation, get [tool][1] to help you change password and then login again...
I have to say that if you can still login pc with admin account, Using "cmd" to change password will be available for you. Or, you can't. You have to refer to pro [Windows Password Recovery Tool][1]...
Check out **Windows Password Recovery Tool 3.0**, it's a program that allows you to [recover your forgotten Windows 8 password][1] without having to reinstall anything...
