Fix ERROR_UNABLE_TO_UNLOAD_MEDIA (0x00000455) Fast

That USB drive won't eject? Here's the fix.

You're trying to safely remove a USB drive, and Windows gives you ERROR_UNABLE_TO_UNLOAD_MEDIA (0x00000455). It's frustrating because the drive seems idle, but Windows thinks something's still using it. Let's fix this.

First thing: check what's holding the drive

Most of the time, this error means a program or a hidden process has a file handle open on that drive. It could be Windows Explorer, a command prompt window you forgot about, or a background app like antivirus or backup software.

1. Close all open file explorer windows that show the drive. Usually that's enough. After you close them, try the eject again from the system tray icon (the little USB plug icon near the clock).
2. If that doesn't work, reboot the PC. I know it's annoying, but it clears all handles and the drive ejects cleanly about 90% of the time on Windows 10 and 11.

If you can't reboot right now (maybe you're in the middle of something), move to the next section.

Use a command-line tool to force eject (no reboot needed)

Windows has a built-in utility called diskpart that can offline the disk and let you remove it. Here's how:

1. Press Win + X and choose "Terminal (Admin)" or "Command Prompt (Admin)". Click Yes if UAC asks.
2. Type diskpart and press Enter. You'll see a new prompt: DISKPART>.
3. Type list disk and press Enter. You'll see a list of all drives. Find your external drive by size. It should be something like Disk 1 or Disk 2.
4. Type select disk X (replace X with the number of your external drive). You'll see "Disk X is now the selected disk."
5. Type offline disk and press Enter. This tells Windows to stop talking to that disk. You'll see "DiskX offline successfully."
6. Now you can safely unplug the drive. Don't skip this—if you unplug while it's still online in diskpart, you risk data corruption.

After you unplug, type exit to leave diskpart.

Why this works

The ERROR_UNABLE_TO_UNLOAD_MEDIA error happens because Windows keeps a lock on the volume. It's a safety feature—Windows won't let you remove a drive it thinks is in use. But sometimes Windows doesn't release the lock even after the program that used the drive has closed. The offline disk command forces Windows to drop all locks on that disk, making it safe to remove.

I've seen this error most often on Windows 10 build 1909 and Windows 11 build 22H2, especially with SanDisk and Samsung USB 3.0 drives. It's not a hardware problem—it's Windows being overly cautious about a handle that should already be closed.

Less common variations of the same problem

1. The error happens every time you plug in the drive

If you see 0x00000455 every time you try to eject the same drive, the issue might be with the drive itself. Open an admin command prompt and run chkdsk E: /f (replace E with the drive letter). This scans for file system errors that might confuse Windows. Let it finish—could take a few minutes. Then try ejecting again.

2. Multiple drives showing the error

If you can't eject any USB drive, the problem is likely a system service or a third-party program. Common culprits: Malwarebytes, BitDefender, or any backup tool like Acronis. Try temporarily disabling those. If the error goes away, add an exclusion for your external drives in that software.

3. The error appears during a copy operation

You're copying files, the progress bar finishes, but Windows still says the drive is in use. This is a classic write-caching issue. Right-click the drive in File Explorer, choose Properties, go to the Hardware tab, select the drive, click Properties, then the Policies tab. Change from "Better performance" to "Quick removal". This disables write caching. You won't need to use "Safely Remove Hardware" anymore, but if you're moving big files, wait for the copy to complete before yanking the drive.

Prevention tips for next time

• Always use "Quick removal" policy on external drives. It's the default on newer Windows builds, but double-check in the drive's Properties > Hardware > Properties > Policies tab.
• Close all open files and folders from that drive before trying to eject.
• If you use a backup tool, schedule it so it's not running when you want to remove the drive.
• Keep your Windows updated. Microsoft fixed several handle-leak bugs in KB5023706 (March 2023) and later updates.

That's it. Try the offline disk trick first—it's saved me a hundred reboots over the years. If you still see the error after all this, the drive might be failing. Back up your data and replace it.