A 1 TB WD Elements dropped on the floor. Windows saw the device and lit the enclosure, so the client reasonably assumed the disk was alive and the fault was logical. It was not.
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The drive arrived after an impact while connected. The client's account was that the PC still recognised the disk and the enclosure lights behaved normally, but no data was accessible.
That combination is worth understanding, because it misleads people regularly. Detection happens over the interface between the bridge board and the drive's electronics. It says nothing at all about whether the heads can read the platters — a drive with a completely failed head stack will still identify itself, report its model and capacity, and appear in Disk Management.
Assessment on the bench confirmed head assembly failure. The heads were not reading, which is why every attempt to access data returned nothing while the drive continued to present itself normally over USB.
The enclosure and bridge board were both functioning. This was entirely a drive-side mechanical fault caused by the impact.
The recovery was completed following the head swap. As with every mechanically repaired drive, the original was treated as a read-once vehicle rather than a disk to return to service.
The client's assumption that detection meant a working disk is the single most common misreading we encounter on impact damage, and it matters because it leads people to run software against a drive that needs to be switched off.
A drive with a dead head stack still identifies itself over USB or SATA. Appearing in Disk Management tells you the interface works, nothing more.
Heads disturbed by a fall drag across the platter surface every time the drive spins up. The damage compounds with each attempt.
An identical model number is not an identical drive. Head count and firmware revision have to match or the replacement stack cannot read the surface.