The short answer
Do not format anything yet. Check whether the drive appears in Disk Management or Disk Utility even without a letter, because a drive that is visible there almost always still has your files. Try a different port and computer first, and treat any prompt to format as a warning rather than an instruction.
A USB drive that does not show up falls into three categories: it is not being powered or detected at all, it is detected but has no drive letter, or it is detected with a damaged file system. Each has a different fix, and the order matters because the wrong first step can destroy recoverable data.
Step 1: eliminate the simple causes
Try a different port
Prefer a port directly on the computer rather than a hub or a monitor. Front-panel ports on desktops are often poorly connected internally.
Try a different computer
This splits the problem immediately. If it works elsewhere, the issue is your computer’s drivers or settings, not the drive.
Check the light on the drive
No light at all points at power or a broken connector. A steady light with no detection points at the controller. A flickering light suggests it is being detected repeatedly and failing.
Listen to an external hard drive
Clicking or repeated spin-up sounds from a mechanical drive mean mechanical failure. Stop immediately and see the warning below.
Remove other USB devices
A bus-powered drive may not get enough current when several devices share a controller. Unplug everything else and retry.
Restart with the drive unplugged
Then plug it in after the desktop appears. This clears a stuck USB stack, which is a real and common cause.
If an external hard drive is clicking, beeping or spinning up and down repeatedly, stop using it. Every additional attempt risks further damage to the platters. If the data matters, a professional recovery service is the correct next step, and continuing to power it on reduces their chance of success.
Step 2: look in Disk Management or Disk Utility
On Windows, right-click the Start button and choose Disk Management. On a Mac, open Disk Utility and enable Show All Devices in the View menu. This shows drives the system can see even when they do not appear in Explorer or Finder.
What you find tells you what to do:
- The drive appears with a healthy partition but no letter. Right-click the partition, choose Change Drive Letter and Paths, and assign one. This is a common and completely harmless fix.
- The drive appears as RAW. The partition exists but the file system is damaged. Do not format. Use recovery software to read the files first.
- The drive appears as Unallocated. The partition table is damaged or missing. Recovery software that scans for lost partitions can often rebuild access to the data.
- The drive appears as Not Initialized. Do not accept the prompt to initialise, which writes a new partition table over the old one. Use recovery software instead.
- The drive does not appear at all. Move to the driver and hardware steps below.
Step 3: driver and system fixes on Windows
- Device Manager, Universal Serial Bus controllers. Look for a device with a warning triangle. Uninstall it and restart, and Windows reinstalls the driver.
- Uninstall USB Root Hubs and restart, which rebuilds the USB stack entirely. They reinstall automatically.
- Disable USB selective suspend in the power plan’s advanced settings. Power saving on USB ports causes intermittent detection failures, particularly on laptops.
- Check Device Manager’s View, Show hidden devices, which can reveal a conflicting entry from an old device holding the drive letter your drive wants.
- Run the hardware troubleshooter, which resolves simple enumeration faults automatically.
Step 4: file system repair, carefully
If the drive is detected with a letter but reports errors, Windows can attempt a repair with chkdsk, and macOS with First Aid in Disk Utility. These are generally safe and often effective for minor corruption.
The important caveat is that repair tools modify the drive. If the data is irreplaceable, make a sector-by-sector image of the drive first, then run repairs on the copy. Free imaging tools exist for both platforms, and this step is what separates a successful recovery from a permanent loss.
Step 5: recovery software
For a RAW, unallocated or unreadable drive, recovery software scans the raw sectors for recognisable file signatures and reconstructs what it finds. It works well for photos, documents and video, less well for heavily fragmented files.
Two rules make the difference. First, recover to a different drive, never to the one you are reading. Second, run the scan once and let it finish rather than stopping and restarting repeatedly.
Flash drives fail suddenly and without warning far more often than hard drives, because the controller is the usual failure point rather than the memory. That is why a USB stick should never be the only copy of anything. If your only copy is on one, make a second copy today rather than after the next scare.
Step 6: when to format
Once you have recovered what you need, or if there was nothing on the drive you cared about, formatting is reasonable. Use a full format rather than a quick one, which checks the sectors and will reveal a drive that is failing physically.
If the format fails, or the drive returns to an unreadable state within days, the controller or the flash memory is failing. A drive in that condition is finished, and no amount of software will change that.
Windows asks me to format the drive. Should I?
No, not while the files still matter. That prompt means the file system is unreadable, not that the data is gone. Run recovery software first and format only afterwards.
Why does my drive work on one computer but not another?
Usually a driver or drive letter conflict on the computer that fails, or insufficient power from that machine’s ports. It is far more often the computer than the drive when it works elsewhere.
Can I recover files from a drive that is not detected at all?
If the drive does not appear in Disk Management or Disk Utility on multiple computers, software recovery cannot reach it. That becomes a hardware repair or professional recovery question.
Does a drive formatted on a Mac work on Windows?
Not if it uses the Mac-only file system. Use exFAT for a drive that must work on both, since it is supported natively by Windows, macOS and most other devices.
How long do USB flash drives last?
There is no reliable figure, and failure is often sudden and controller-related rather than gradual. Treat any flash drive as temporary storage and keep a second copy of anything important.
The safe order
Different port, different computer, restart with it unplugged. Then look in Disk Management or Disk Utility and read what state the drive is in. Assign a letter if that is all it needs. If it shows as RAW, unallocated or uninitialised, use recovery software before touching anything that writes to it. Image the drive first when the data matters. Format only when you have what you need.
