Problem Ejecting USB Mass Storage Device - Try the Task Manager

Wed, 12/07/2017 - 10:34 -- James Oakley
USB Drive

Almost every Windows user is familiar with the problem. You have an external hard drive, or a pen drive, attached to your computer. You know the correct way to eject the device: Don't just yank out the lead, because it could corrupt data if the computer was in mid-write at the time. Instead, use the "Safely Remove Hardware and Eject Media" tool in the notification area of the taskbar.

But then comes the problem:

Problem Ejecting USB Mass Storage Device

Problem Ejecting USB Mass Storage Device
Windows is unable to stop the device 'USB Mass Storage Device'. Don't remove this device while it is still in use. Close any programs using this device and then remove it.

The trouble is, you can't think of any programs using the device. You've closed anything like Microsoft Word, that may have had a lock on a file it was editing on the device. So what do you do? Yank out the cable anyway?

That's what I used to do. In despair, and against my better judgement.

But then, one day, I was looking in the computer's Event Log for something else, and I spotted an event:

  • Event Log = System
  • Level = Warning
  • Source = Kernel-PnP
  • Event ID = 225
  • Message: The application System with process id 4 stopped the removal or ejection for the device USB\{stuff}

Ah. So if I can find what process has ID 4, I'll find which process is preventing removal of the external drive.

To my great surprise, PID=4 was the Task Manager, taskmgr.exe.

Sure enough, in the system tray, there was a copy of Task Manager running. I chose Exit from its menu, and tried to eject the drive. Bingo:

Safe to Remove

Safe to Remove Hardware
The 'USB Mass Storage Device' device can now be safely removed from the computer.

So next time you inexplicably cannot remove an external drive, look and see if the Task Manager is running. And if it is, close it and try again.

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