I have a macbook 2 years old it suddenly gave me the grey screen with question mark. So I work a lot with PC laptops so i replaced the harddrive with a clean laptop drive. I even erased it in disc utility on my macbook pro. When installing the OS it does not find the harddrive. Is it possible im doing something wrong, or is the sata port possibly the problem. I tried installing the OS with the hard drive connected USB ( i have a SATA to USB cord) it would see the hard drive but wont let me install. Thanks for your time.