I am trying to install a 1TB WD Scorpion Blue into a friends 13" MBP. His computer refuses to start up with the new drive installed, giving the black dialogue box on top of a grey screen with "you need to shutdown...hold down the power key... etc." in five different languages. His computer also won't boot from a retail SL disk (version 10.6). We have tried zapping PRam, no luck. Using my 15" MBP, we successfully installed SL onto the new 1TB disk using an external USB to ATA adapter. Booted from the 1TB disk successfully onto my 15" MBP using the USB to SATA connector. Yet still, his computer still refuses to boot from the new drive, giving the same message "you must shutdown." Any ideas why his computer refuses to boot from this new disk or a retail copy of 10.6?? This is blowing my mind... We reinstalled his stock HDD for now and his 13" is running fine.