Just like you are not supposed to switch off the power to your computer and walk away, you are not allowed to pull out a USB device that is in use, because such rash behavior may corrupt the data on the drive or it may even damage it. There is a procedure to safely remove a connected USB hardware such as Flash drive or external hard disk, one that I assume every user is aware of. Now every so often Windows is unable to let go the drive. This happens when some process is still reading data from or writing data to the USB drive, and when that happens Windows displays a message such as the one below.
Generally, people attempt to safely remove the drive (using the icon in the system tray) a few more times and when that fails they yank out the drive anyway or shutdown the computer and then remove it. The second option is definitely safer and a non issue if you are going to shutdown the computer after taking out the drive anyway. But the correct method is this:
- Open Device Manager from the Control Panel. You can get to the Device Manager quickly by opening the Run box from the start menu and by typing Devmgmt.msc.
- On Device Manager, expand the Universal Serial Bus controllers. There you will find listed all USB devices connected to the machine. The list doesn’t identify which device is what. Flash drives and external drives will be listed as USB Mass Storage Device.
- Right click on each USB Mass Storage Device and select Disable. Now you can pull out your USB drive.
The problem with this method is, like I said, you cannot identify the devices from the list. If you have more than one Flash drive connected you have no option but to disable all USB Mass Storage Devices. Dev Eject offers a solution.
Dev Eject is a small free program designed for easy management of removable media connected to your computer, and the most useful feature in the context of this article is that it allows us to see all processes that are using a USB drive and hence preventing its safe removal.
When you start Dev Eject, it will displays all devices connected to the machine via USB. Select the device that Windows is not allowing to remove and click on the ‘Locks’ button. This will show a list of all the processing currently using that drive. Once you get the list of processes you can easily close the offending programs and safely eject your drive.
In the example shown above, a Word file is locking the USB drive. I just have to close it and the device can be safely removed.
Related Reading: Control USB drive letter assignment in Windows with USBDLM