Hello,

I posted this message in the WD community board as well, I really hope that someone can help.

HDD:
WDEARS - 00z5b1
1.5 TB SATA 64MB Cache
Circuit Board: 2061-701640-807

The drive was mounted in an external inclosure so that I could backup its contents to another external drive, when it suddenly failed
Some critical files were not backed up.

Status:
The drive spins up. I can feel and hear the motor. But that's it.
It's no longer recognized by my computer's BIOS (ASUS motherboard), or by any of my eSATA or USB external enclosures.
If the motherboard could simply recognize the drive I would use UNIX or DOS based recovery software to produce an image while I tried to recover data from it, but no luck.

So, does this mean that the problem is related to the circuit board? Can I replace it? Could it be a connector or some other electrical issue? How do I diagnose and fix the problem?

Any and all help would be very much appreciated!

Thank you. (but no smiley face cuz I need those files)

If the files are as critical as you imply, there are data recovery companies that will be able to help you. There is nothing that you posted that can diagnose the problem so far. I advise to contact one and hopefully the costs are not high because you haven't made it any worse by trying homebrew methods.
If you put the drive in a PC and connect it via sata, try seeing if DMDE(free) can see the drive. Ignore what your motherboard or windows says, just see if it is seen by DMDE. If not, I advise for you to take to a DR place.

Thank you. After reviewing my original post, i think that I should clarify the steps that I've taken.

At first, I was optimistic and I tried using different eSATA and USB enclosures (under Windows), but that didn't work.

Then I installed the SATA drive in my desktop PC (even tried different SATA cables on SATA1, SATA2, etc. but the motherboard / BIOS cannot detect the drive or identify it.

I'd think it was completely dead, except that the drive does seem to spin up.

Question: would DMDE or other low-level HDD tools (on a linux or dos bootdisk) be able to see a drive when the BIOS/motherboard itself cannot?

As for data recovery/hdd repair services, aren't they really expensive?