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My mid-2009 MacBook Pro was getting slow with its 750 GB hard disk, so I decided to upgrade to a San Disk X400 1TB SSD. I formatted the disk using a Sata to USB cable, clean installed Mavericks and used migration assistant to transfer my files. I can boot the laptop from the drive just fine using the USB cable. However, when I connect the drive internally, it won’t boot. If I then connect the old 750 GB drive to the USB cable and boot it from the old drive, the new drive shows up on the desktop, but I can’t open it or otherwise do anything with it. SanDisk thinks my computer may not accept a drive that size (that 1TB is too big!) but I don’t think that’s right. Can anyone help me out with this?

You have a known issue! Your HD drive cable needs to be replaced here. The issue here is the drive cable you currently have is SATA II (3.0 Gb/s) which is fine for your old SATA II HD. But now you’ve put in a SATA III (6.0 Gb/s) SSD which is having problems with the old cable. Here’s the part you need: MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable - Apple P/N 923-0104. Don’t use the older version of the cable! And here is the IFIXIT guide you’ll need to follow: MacBook Pro 13" Unibody Mid 2009 Hard Drive Cable Replacement. You also may want to check your systems firmware: About EFI and SMC firmware updates for Intel-based Mac computers. Make sure you’re at the level listed or newer.

No need any SATA to USB cable. Just use a OS X installation USB drive to boot up the computer and use Disk Utility to make partition and format the drive. Then you are done. X400 SSD is compatible with SATA 3.0 Gbps and 1.5 Gbps