Data Recovery Case File · Mac & Apple Ecosystem · The Machine Changed, Not the Drive

It Worked Until I Used a Newer Mac

Her enquiry contained a sequence that people rarely think to report and which changes where to look first. A WD Passport for Mac holding all her photographs: "It has always worked, but I plugged it into a new Mac and it is now not registering, and a white flashing light is showing. Someone has suggested this may be corrupted." The suggestion may be right. But before accepting it, there is a question worth asking that costs nothing: what changed was the computer, not the drive — and newer operating systems have quietly dropped support for things older drives rely on. A drive that has "always worked" and stops on first contact with a new machine deserves that possibility ruled out before anything else.

The decode: the free question first, then the drive

What may have changed on the computer's side: macOS has progressively withdrawn support for older technologies, and two matter here. Newer versions have dropped or reduced support for some older filesystems, so a drive formatted years ago in a scheme the new machine no longer reads will appear as an unrecognised device rather than as a working drive. And drives that relied on the manufacturer's own utility or encryption software can stop being accessible when that software no longer runs on a current system — which is a licensing and compatibility problem rather than a data one.

Why that possibility should be tested first: because it is free and it changes everything. If the drive still works on her old Mac — or on any other computer — then nothing is wrong with it and the answer is to copy the contents off using the machine that can read it. That single test costs nothing, takes minutes, and either eliminates a whole branch or confirms it. Anyone who has just moved to a new machine and found a drive unreadable should try it on the previous one before assuming failure.

Why "someone suggested corruption" is worth testing rather than accepting: corruption is the default explanation people reach for, and it is often right — but it is a conclusion rather than an observation. A drive that is genuinely corrupt behaves the same way on every machine. A drive that is fine and simply unreadable by one operating system does not.

What the flashing light adds: a useful piece of drive-side information. An indicator that flashes continuously while nothing is accessing the drive is not activity — it is the drive attempting its readiness sequence repeatedly and not completing it. If that is happening on every machine, the fault is in the drive rather than in the host's support, and it points at head calibration or the reserved firmware region. So the light and the cross-machine test together separate the two branches cleanly.

What to avoid while establishing which: the new Mac may offer to initialise a drive it cannot read — and on a perfectly healthy drive whose filesystem is simply unsupported, accepting that would destroy everything for no reason at all. Nothing should be initialised, erased or repaired until the branch is settled.

On the bench

The free branch was tested before anything else: the drive tried on its original machine and on other hosts, since a drive that works elsewhere has a compatibility problem rather than a fault, and the answer is then to copy from the machine that reads it. Where the drive failed everywhere, it was read write-blocked on native equipment and its filesystem identified independently of any host's support — which distinguishes an unsupported-but-intact volume from a damaged one. Where structures proved damaged, they were reconstructed on the image rather than the original, and the photographs validated by rendering.

The outcome

The compatibility branch eliminated first at no cost, the filesystem identified independently and the contents recovered and validated. Free assessment, one fixed written figure including VAT, no recovery, no fee. The decode, for anyone whose drive stopped when their computer changed: what changed was the machine, so test the drive on the old one before assuming failure — newer operating systems have withdrawn support for some older filesystems and for manufacturer utilities, which makes a perfectly healthy drive appear unreadable; a drive that works on any other computer has a compatibility problem and the answer is to copy from that machine; a continuously flashing light while nothing is accessing it means the drive is retrying its own start-up, which points the other way; and never accept an offer to initialise while you are still working out which.

Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.