I have a 13 black macbook. Its an older one but the other night i went to turmn it on and the grey screen with the apple logo comes up with the little twirly thing and stays for about a minute then it shuts off. I replaced the HDD last November I want to say. When the first one went there would be a clicking noise which I am not getting now. I suppose I will try taking out the ram and HDD and reinstalling them. I am looking for my OSX disk as we speak. Any other suggestions or does anyone know what may have happened.