PC Fix"USB device not recognised" and drives that do not appear
Rule out the port and the cable first. Then check whether Windows sees the device but has not given it a drive letter.
What you seeUSB device not recognised. The last USB device you connected to this computer malfunctioned
1. Port, cable, other computer
- Unplug and plug in again, firmly.
- Try another USB port, directly on the computer. On a desktop use the ports at the back. Avoid hubs and extension cables for the test.
- Try another cable, for devices with a detachable one. Many phone cables charge but carry no data.
- Try the device on another computer or a TV. If it fails everywhere, the device is at fault, not Windows.
- Restart the computer with the device unplugged, then plug it in.
For a portable hard disk that clicks or spins up and down, the port is not giving enough power: use the port with a lightning or battery mark, a Y-cable, or a powered hub.
2. Does Windows see it?
Right-click Start › Disk Management. Look at the lower pane for your drive.
| What you see | Meaning | What to do |
|---|---|---|
| The drive with a blue bar but no letter | Windows sees it but has not named it | Right-click the blue bar › Change Drive Letter and Paths › Add › pick a letter |
| Offline | Disabled by Windows | Right-click the disk's name on the left › Online |
| Unallocated (black bar) or RAW | No readable file system: new, or damaged | If it holds files you need, do not format; see below. If it is new or empty: right-click › New Simple Volume |
| "Not Initialised" | The partition table is unreadable | Same caution: initialising a disk that held data erases the map to it |
| Nothing at all | Windows does not see the device | Go to step 3 |
A phone that does not appear needs its USB mode changed: unlock the phone, pull down the notification shade, tap the USB notification and choose File transfer. iPhones ask you to tap Trust.
3. Refresh the USB drivers
- Right-click Start › Device Manager. Expand Universal Serial Bus controllers. A device marked "Unknown USB Device (Device Descriptor Request Failed)" with a yellow mark is your culprit.
- Right-click it › Uninstall device. Unplug the device, restart, plug in again.
- If that does not help: right-click each USB Root Hub › Properties › Power Management › untick "Allow the computer to turn off this device to save power".
- Turn off USB selective suspend: Control Panel › Power Options › Change plan settings › Change advanced power settings › USB settings › USB selective suspend setting: Disabled.
- Install chipset and USB drivers from Settings › Windows Update › Advanced options › Optional updates, or the computer maker's support page.
- Turn off Fast startup (Control Panel › Power Options › Choose what the power buttons do) if the fault appears only after shut-down and start, not after Restart.
4. The drive appears but will not open
"You need to format the disk in drive E: before you can use it" means the file system is damaged. Click Cancel. Then, in Terminal (Admin), try a repair, using the drive's letter:
chkdsk E: /fIf chkdsk says the type of the file system is RAW, it cannot help. Files may still be recoverable with recovery software or a data recovery service, provided nothing new is written to the drive. See deleted files recovery.
5. Protecting drives in future
- Use Safely Remove Hardware (the USB icon in the tray) before pulling out a drive, above all after copying.
- Do not unplug during a copy, and do not move a spinning hard disk.
- Keep a second copy of anything that matters. Pen drives fail without warning.
Why does my pen drive work on other computers but not on mine?
The USB port, its driver or a power-saving setting on your computer is at fault. Work through step 3.
The drive shows the wrong size or 0 bytes. What does that mean?
The drive's controller has failed, or it is a counterfeit drive that misreports its size. Files on it are usually not recoverable at home.
For Windows 11 and Windows 10. Written in November 2026. Menus move between updates; use the search box in Settings if a name differs. Back up important files before any step that resets, repairs a disk or opens the computer. This is an independent guide, not connected with Microsoft.