I have two hdds in it one held my operating system and the other was used for backup, but actually came out of my old ASUS Rog computer and still had the win 7 os on it. when I turned on the pc that os came on and the other drive seemed to be missing, checked the HDD and it runs fine on another PC, then the next thing I knew my G75VW didn't see any hard drive in the BIOS, What the heck, I have ghosts in this machine.