How to Fix Unrecognized USB Devices on Windows

When USB devices such as flash drives or external hard drives are not recognized on your Windows PC, the issue can stem from insufficient power, BIOS settings, driver problems, or registry misconfigurations.

First, open a command prompt (Start → Run → cmd) and execute the following commands to expose hidden devices in Device Manager:

reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v "DEVMGR_SHOW_DETAILS" /d 1 /t REG_SZ /f

reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v "DEVMGR_SHOW_NONPRESENT_DEVICES" /d 1 /t REG_SZ /f

Restart the computer, then open Device Manager, choose View → Show hidden devices, and uninstall any greyed‑out USB controllers or USB mass‑storage devices. Afterward, right‑click the "Universal Serial Bus controllers" node and select "Scan for hardware changes".

If the problem persists, open the registry editor (Start → Run → regedit), navigate to

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E967‑E325‑11CE‑BFC1‑08002BE10318}

, and delete the "UpperFilters" and "LowerFilters" values.

Additionally, for each USB Root Hub, open Properties → Power Management tab and uncheck "Allow the computer to turn off this device to save power".

Hardware‑related possibilities include: BIOS disabling USB (enable it in BIOS), using the wrong USB port (try rear motherboard ports), insufficient USB voltage, motherboard‑system compatibility issues (BIOS update), a damaged USB device, or faulty USB drivers.