Your drive is not encrypted. However, the reason you are being prompted to format it is that the partition table is set up for a 4Kn drive rather than 512e.

Notice that the first partition is reported as having a size of 500GB. This is because the sector size is now 512 bytes whereas inside the enclosure it was 4096 bytes. Also, the beginning of the partition is sector 256 when the drive is inside the enclosure but 2048 (= 256 x when connected to your motherboard's SATA port.

976745984 sectors x 512 bytes per sector = 500GB

976745984 sectors x 4096 bytes per sector = 4TB

Windows can see the partition table in sector 0, so that's why you were not being prompted to initialise your drive. However, Windows is looking for the boot sector in the wrong place, so that is why it is prompting you to format the partition.

Really, all you need to do is to locate a non-encrypted bridge board from a My Book (not a My Book Essentials) and ensure that it was mated with a 3TB drive or greater. A 2TB external will probably be configured with a 512-byte sector size.

BTW, there are plenty of 3rd party enclosures that are configured with 4Kn sectoring, but their poor documentation makes it difficult to identify them.

_________________
A backup a day keeps DR away.

So at this point, getting a copy of the original bridge, which might be encrypted, would be a backwards step?

Also, is there any chance that 3rd party software can instruct Windows to read the drive in 4Kn segments instead of 512? Or is this absolutely a hardware issue, as in, it doesn't matter what I tell Windows to read because the HDD sends at 512 in the absence of the enclosure?

Encryption relies on a "key sector" which is stored at the end of the drive's user area. This "Smartware" area is hidden from the user by the bridge firmware. I don't know enough about this feature to be able to tell you whether a board from an encrypted enclosure will work with your non-encrypted drive. It could be that an "encrypted PCB" may simply revert to non-encrypted mode if it doesn't find a key sector, but I don't know. That's why I'm suggesting that it would be safest to stick with a My Book PCB rather than an Essentials, but I don't know how to tell the difference, assuming there is one, just by observing the board on its own.

As for software that can deal with your 512e/4Kn mismatch, perhaps R-Studio can do it. Otherwise I know that DMDE can recover data from a 4Kn image file, but you would need to ask its author for advice in your specific situation.

_________________
A backup a day keeps DR away.

I downloaded R and R-Studio over the weekend based on the thread you linked - I'm assuming I would need a disk recovery "package" for that?

I would ask R-Studio's support rep, "Alt(R-TT)":

memberlist.php?mode=viewprofile&u=18257

_________________
A backup a day keeps DR away.

Try it in demo mode first.

_________________
PC Image Data Recovery
http://www.pcimage.co.uk

New!! HDD-PCB.COM for all your PCB and donor HDD requirements!

I have attached a SS of R-Studio, it is nearly done scanning the drive. It's found FAT Boot, Specific File Documents, n and a few UFS/FFS Cyclinder groups - does that sound reasonable?

FWIW, last night I tried to scan using DMDE, Recuva, and GetDataBack with no luck (No File Structure Found). R-Studio seems to at least recognize the 4K and that the drive has BitLocker on it, which I make as being a positive re: hardware and a negative re: software (where would I enter the password? I know it even!).

So, as an update, this didn't work. The finished product of the scan looked more or less like the above, but the file structure couldn't be read.

Disk Management says that the drive is "Healthy," but also "RAW." In case this is a bitlocker thing, I'm currently running repair-bde to see if I can't unlock it.

Thank you for this. I realize I downloaded the wrong thing now. I had RStudio, which I realized wasn't R-Studio when looking for the Disk Drive Management interface.