Windows Easy Transfer (WET) Issues with External Hard Drive - "Can't read from the source file or disk"

Question

I work for Office Depot, in the tech department. Basically, one of our associates was supposed to do a data backup, and re-install Windows 7, then transfer the files back. He used Windows Easy Transfer and compacted everything into a 163 GB file. 
Now comes the hard part. When we try to put it back on his computer ((drag-and-drop to the desktop) which has been wiped back to factory settings using the recovery partition), it stops at 79.5 GB remaining (you know how it doesn't give you a % of completion,
it just shows how many GB are remaining) and then says "Can't read from the source file or disk" and gives you an option to try again, or cancel. It gets hung up on the same point each time.
Normally, this wouldn't be a huge issue, but the contents on the drive are his wife's architect blueprints and interior design stuff, along with wedding photos, etc, which are the only copies they have. On top of those, they have court documents and other
important files that we are unable to access now.
I wasn't involved with this transfer, so I'm trying to clean up the mess as best I can. I remembered that the customer's wife was Russian, and had some files typed with a Russian keyboard, so on and so forth. I wonder if that's the issue? If not, I really
have no idea how to manually extract things from a ".mig" file, or how to diagnose what area is potentially corrupted.
In light of this situation, we tried using "Recuva" to recover the files post-wipe, but everything was corrupted or unable to be opened, and it also extracted and recovered all of the "useless" photos, such as the skype logos, up and
down arrows for browsers, etc (it was 160,000+ photos).
Trying to avoid a potential lawsuit, unhappy customer, and costing the company lots of money to see if professionals can get into this external hard drive.
Other relevant information:
We used a Toshiba 500 GB (465 GB) external hard drive.
Customer's computer is an HP Pavilion P6000 Series (Model No. p6520y) running Windows 7 Home Premium 64-bit Service Pack 1.
Any other information that is needed can be provided, thanks in advance, and hopefully we can find a solution to this issue quickly!
-John

Answer 1

I think there's a lack of understanding somewhere.
"If you even can't start the process, please unplug it from your new PC. Then head back to your new computer and plug
the external drive back in to your new computer. "
Unplug from new, head back to new, plug it back in? That doesn't make much sense! Haha.
I knew what you meant though, somewhat. When I search through the drives after clicking yes (Has windows easy transfer
already saved your files blah blah blah) I click on the transfer file and it says "Windows Easy Transfer could not open the file".
Rather than drag-and-drop the file to the desktop, I now tried to double-click on the file itself while it was plugged
into the computer. It opened, and it started transferring until it was about 70% completed, and then an error popped up saying "WET can't open the easy transfer file, make sure your USB device is plugged in or check your internet connection". 
I checked, and the USB hard drive's light wasn't on. Now, I unplug it and plug it back in, and the light comes back on,
so I click Retry, and it resets the bar back to nothing and says "Transfer time: 1 minute".
Rather than continue trying, I clicked "Cancel" instead of Retry, and it says "Your transfer did not complete successfully."
It says to click "view report" for more information, but there's no "view report button".
At the moment, I am scanning the External Drive for bad sectors using the check disk tool in properties. It's frozen
at "0 USN bytes processed".