Hey, i have a problem i have a old white macbook that i got from my mom cause she didnt used anymore. I have my own macbook pro. I used the Hard Drive of the old macbook and i formated it to use it als external HD. Now i want to reboot the old macbook and use it as a extra macbook but because i erased everything from the HD it won't work. when i put the HD in there is a question mark folder. PLEASE HELP I TRYED EVERYTHING !