Bruntsfield calls on this one are usually a variation of the same setup: a resident on Bruntsfield Place who has just bought a new laptop and cannot open the old drive on it, a small design studio near the Links whose freelancer’s external SSD reads fine on their MacBook but locks the office Windows PC out, a student on Montpelier who copied a dissertation onto an external drive at home and hit Access Denied when they plugged it into a library computer the next morning. The plot is always the same. The drive works on one machine and not another. Nothing was dropped. Nothing was ejected badly. Yet one PC opens every folder and the other one refuses to show a single file.
Nine times out of ten, the drive itself is completely healthy. What you are looking at is a permissions, encryption, or filesystem quirk between two Windows installs — and each cause has a specific fix that takes minutes if you know which one you are dealing with. This guide walks the five real causes we see on the bench, in the order to rule them out. If the drive holds anything you cannot afford to lose, stop and read the last section first, then come back — the wrong fix on the wrong cause can turn a five-minute job into a proper data recovery in Bruntsfield case.
Before Anything Else — Confirm It Really Is Windows and Not the Drive
Before touching permissions or drivers, spend two minutes ruling out the drive itself. Plug it into the PC where it does not work and open Disk Management (right-click Start → Disk Management). If the drive shows up there with a healthy partition and a drive letter, the hardware is fine and File Explorer’s Access Denied is a software problem — skip to step 2. If the drive appears as “Unallocated”, “RAW”, or does not appear in Disk Management at all, that is a different guide entirely: work through the external hard drive not recognised checklist before you go any further, and if the drive is clicking or beeping stop powering it on immediately (see the clicking external drive post).
On the bench, this is the point where I’ll also plug the drive into a Linux boot USB — not because customers should, but because if a Linux live session reads every file cleanly, that is the deciding proof that the drive, the cable, the enclosure and the filesystem are all healthy. From there, every remaining cause is Windows-side and safe to fix without a recovery image. If you would rather we make that call for you, that is what our workshop 20-minute check is for.
1. NTFS Permissions Carrying an Old Account’s SID
This is the single most common cause in Bruntsfield — a resident replaces a laptop, moves the old drive to the new one, and File Explorer shows the folders but throws Access Denied the moment they try to open one. NTFS stores permissions against the numeric ID (a “SID”) of the user account that owned the file, not against their username. When the old laptop is gone, so is that SID, and the new laptop looks at the folder and sees a permission entry it cannot resolve to anyone. Windows quite correctly refuses to open it.
The fix is Take Ownership. Right-click the top-level folder on the drive → Properties → Security tab → Advanced → the “Owner” line at the top → Change → type your current username → OK → tick “Replace owner on subcontainers and objects” → Apply. On any drive with a lot of files this can take five to fifteen minutes; leave it. Then, back on the Security tab, click Edit and add your current user with Full control if you cannot see it in the list. Every folder that was locked will open normally afterwards.
If you are comfortable at a Command Prompt, the two-line version is faster and more reliable: open an elevated Command Prompt, run takeown /f E:\ /r /d y to change ownership recursively, then icacls E:\ /grant %USERNAME%:F /t to add yourself with full permissions (swap E: for the drive’s letter). The exact scenario is what we walked through in the old hard drive access denied post — different failure surface, same underlying cause, so worth reading before running the command if the drive is IDE from an old desktop rather than USB.
2. BitLocker To Go Waiting Quietly for a Password
This one catches people out because the drive does not look encrypted. The tell is subtle: the drive icon in File Explorer has a small gold padlock on it, or the drive shows in Disk Management as “BitLocker encrypted”, but on the PC where it works you have never been asked for a password because Windows saved it after the first unlock. On the second PC, BitLocker prompts for the recovery key or the password on connect — and if the prompt has been dismissed or the notification is not showing (a common gotcha on managed office builds where notifications are suppressed), the drive just sits there refusing to open.
To check, plug the drive in and look for the BitLocker prompt in the system tray. If nothing appears, open Control Panel → System and Security → BitLocker Drive Encryption and look for the drive under “Removable data drives”. If it is encrypted, click “Unlock drive” and enter the password. If you do not remember the password, you need the 48-digit recovery key — it will be tied to whichever Microsoft account was logged in on the PC that first encrypted the drive, and lives at account.microsoft.com/devices/recoverykey. Without the recovery key, the encrypted contents are genuinely unrecoverable — not by us, not by a lab, not by anyone. Chase the key first, always, before considering the drive lost.
3. exFAT and NTFS Driver Quirks Between Windows Versions
This one is quieter but very common when the two PCs are running noticeably different Windows builds — a home laptop on Windows 11 24H2 and an office desktop still on Windows 10 21H2, or a small-business machine that has been left on an older LTSC build. Two specific patterns turn up:
First, an exFAT drive formatted on a Mac or a modern Windows install with a large cluster size (128 KB or above) will sometimes read for the file listing on an older Windows exFAT driver but throw “the file or directory is corrupted and unreadable” on the actual file open. Nothing is corrupted — the driver just does not handle that cluster geometry. Copying the drive on the newer machine to a fresh exFAT volume with the default cluster size fixes it permanently.
Second, an NTFS drive that was quick-formatted with a compression flag set (an unusual choice, but we see it) will read the directory tree on any Windows install but refuse to open individual files on machines where the NTFS file system filter for compression is disabled by group policy — more common than you would think on managed corporate laptops. Right-click the folder → Properties → Advanced → untick “Compress contents to save disk space” on the good PC, and the files copy off normally afterwards. A proper repair of that class of issue often sits alongside our software troubleshooting workflow rather than any hardware work.
4. USB Power and Bus Negotiation on 2.5″ Bus-Powered Drives
If the drive is a portable 2.5″ spinning hard disk (not a solid-state one, and not a 3.5″ desktop drive with its own power brick), and the “working” PC is a laptop while the “not working” PC is an older desktop — or vice versa — the culprit is often USB bus power rather than the drive itself. A 2.5″ portable drive needs a stable 5 V at up to 900 mA on spin-up, and older desktops with a lot of USB devices already drawing power, or laptops with worn USB ports, can quietly under-deliver. The drive spins up enough to enumerate but not enough to hold data reads open, and File Explorer times out with vague errors that read like a corrupt filesystem.
The test is straightforward: plug the drive into a powered USB hub (any brand with its own mains adapter) between the drive and the problem PC. If the drive suddenly reads normally, USB power is your answer — either keep using the hub, use a Y-cable that draws power from two USB ports at once (they come with most 2.5″ drives new), or plug into a USB port on the back of a desktop rather than a front-panel or hub port, which almost always provides more stable current. This is also the cause we see on drives that read fine at home on a laptop and fail as soon as they touch an office docking station — docks are notorious for weak per-port USB current under load.
5. A Drive Letter Conflict — The Office-PC Special
Worth a paragraph on its own because it is entirely invisible from File Explorer: on the PC where the drive does not open, Windows may have quietly assigned it a drive letter that is already claimed by a mapped network drive from the office server, or by a phantom letter left behind by a previous USB device. File Explorer shows the drive; opening it either returns Access Denied (because it is really trying to open the mapped network share you no longer have permission for) or hangs on the network timeout.
Open Disk Management, right-click the drive’s partition, choose “Change Drive Letter and Paths…”, and reassign it to a letter you know nothing else uses — K:, R:, or Z: are usually safe. The drive opens instantly. This is worth checking on any small-business PC that has a login script or Group Policy mapping several network drives, and it is one of the fixes we run as a matter of course when a client calls us for business IT support on a shared-drive complaint.
When to Stop and Bring the Drive In
Stop and bring the drive to us if any of the following is true: the drive is clicking, beeping, or spinning up and down; Disk Management shows the partition as RAW or Unallocated when it used to work; you have already tried a partition-recovery tool (Recuva, EaseUS, MiniTool) and files are now showing up half-named or in the wrong folders; the drive is BitLocker encrypted and you do not have the recovery key. In every one of those cases, a technician working on the drive without imaging it first can burn the last chance you have — and the file that mattered is often the one that goes.
What we do on a workshop drop-off is image the drive first (bit-for-bit, to a spare disk of the same size or larger) and then run all the same permission and encryption checks above on the image rather than the drive itself. If a fix works on the image, it works on the drive too; if it destroys the image, the drive is untouched and we start again. Bruntsfield drop-offs go straight into the same-day queue if they come in before lunchtime — the shop is on Parkhead Drive off the west side of Slateford, a quick number 4 or 44 bus from the Links, and we can also come to you as a home or office callout if the machine is a desktop that cannot easily be brought in. Whether you are in Bruntsfield, up in Marchmont, across in Tollcross, or over towards Fountainbridge, the workflow and turnaround are the same.
Last updated: 20 September 2026