Ok, I have an unique issue. First off, I have tested all the hard drives and the SATA flex cable. I have two drives, both Seagate 500Gb OEM Apple hard drives. I can plug both drives in my other Macbook and mount, erase, format and partition just fine as an external drive. I install it in the Macbook in question, it takes 5 minutes to unmount, then hours to partition. I started my last test 4 hours ago, the blue status bar is still moving and the time shows: Estimated Time 1 hour 47 Minutes. I have followed these steps: I plug in other Macbook and format as external. I install hdd into macbook in question. I boot from Mountain Lion Disc (OEM) I go to install, and the drive does not show up at all. I go to Disc Utilities and the drive is visible. I erase and format, but just sits there all day. I cannot see how the problem is the flex, I have two exact same Macbooks and the flex and hard drive works just fine in the other one. Ive done all the basic resets too... So my question is, what else could the issue be? It is almost 6:00pm and I started this format after lunch. its been at least 4 hours.