I have a late 2011 Macbook pro with OS 10.8.4. I just bought a brand new HGST Travelstar 1tb internal hard drive with a OWC enclosure that replaces the optical drive in my MacBook Pro. After following all the steps and correctly installing the hardware the computer says that the hard drive that I am using isn't readable in my computer. I figured it said that because I have to format it in Disk Utilities to Mac OS extended. Disk Utilities recognizes the hard drive but when I format it half way through it gives me an error message. After doing some research I figured let me try using Disk Warrior on the brand new blank hard drive. DW got stuck on step 5 and it is currently running. So far it has 552 malfunctions. I'm not sure if the Hard drive is not compatible in my laptop or it's defective.