"Device Not Ready" error message.

Testing the external enclosure's hard drive.
The external enclosure's circuits may be damaged.
You MAY need to buy a new external enclosure, or connect the drive internally to a computer, before you can attempt to repair the data damage.
If you have another drive you can install in it so you can test whether the enclosure works fine, try that.
If you can't do that and have any doubts about that, connect the drive internally to a computer before you attempt to repair any data damage. According to my experiences you can't run the hard drive manufacturer's diagnostics on the hard drive when it's in the USB enclosure.
Testdisk - get the Stable version:
http://www.cgsecurity.org/wiki/Test...
Glary Undelete:
http://glary-undelete.en.softonic.com/
PC Inspector (freeware)
http://www.snapfiles.com/get/pcinsp...
Zero assumption Recovery
http://www.z-a-recovery.com
The demo is limited
It will only recover 'up to' four folders per run
But you can make multiple runs
Really good, but you have to pay for it.
GetDataBack
http://www.runtime.org/
.....
Lots of file recovery programs
...................

Apparently, the Windows version of Seagate's SeaTools can test any hard drive brand when it's in an external enclosure.(The bootable Dos version of it CANNOT.)
Do the long test.
SeaTools
SeaTools for Windows

System Requirements:

• Microsoft Windows 7, Vista, XP or 2000.
• Microsoft .NET Framework v4.0 - Available for download (approximately 48 MB) from www.microsoft.com. Search the site for .NET 4.0 or go directly there.
• VGA 1024x768 or greater graphics capability.

SeaTools for Windows tests SATA, USB, 1394, ATA (PATA/IDE) and SCSI drives. It installs onto your system. SeaTools for Windows is completely data safe.
 If the drive passes SeaTools for Windows, your troubleshooting can move to other areas.

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