Cannot remove USB drive W8.1 device in use

Usually that is because something is accessing the external disk. Close all programs that may be accessing it, or make sure they are pointed at some other location. Also check your AV settings, some of those tools may be scanning the disk at the time you want to remove it.

Download Sysinternal Process Explorer.

Run the program as an administrator (right click on icon and click run as administrator).
Press ctrl+f and type the drive letter and colon.

A list of processes will display and will show you the process with the handle on the drive or file in the drive. Remember the PID and close the search window. Find the process and its sub-processes and determine which one to either close or force close.

I was going to include "shutdown the computer and then pull the USB device."
in my comment... but it is a time consuming work around and not a solution that helps.

If you want to be 100% safe & sure then use the free unlocker:

http://www.emptyloop.com/unlocker/

Another download link for unlocker:
http://www.softpedia.com/get/System/System-Miscellaneous/Unlocker.shtml

There is more detail on this subject in this article from pcworld.com:

http://www.pcworld.com/article/2040932/how-to-safely-remove-a-usb-drive-even-when-windows-says-it-isnt-safe-to-do-so.html

it could be the searchindexer that is accessing the drive

I would suggest you try setting the disk offline in disk management.

Win + X
Disk Management
Right-click the disk number in question
Check properties to ensure the model matches the external you're wanting to set offline
Right-click > Offline
This should allow the disk to be removed, but is only a little safer than simply pulling the plug.

You could go with the recommendation posted by Spencer George as well, as this could also clue you in on a specific process that is regularly causing the issue.

if you right click the drive ) can you select "eject drive" ?

Thanks all for your suggestions. By now I've tested some without succes: I've disabled searchindexer, Antivirus and any program on TaskManager that I could identify. There are not any software running but I cannot remove the USB external HD.

Process Explorer is a nice sotware and has identified a handle TxfLog. I'm reading about this problem and I'll try another of your suggestions.

Good luck,,,, just pull the USB plug and move on.
No harm will occur if you are not presenttly writing to the USB drive,

nobus

if you right click the drive ) can you select "eject drive" ?

I can't see the Eject option if I right click the drive

Jim_Nim

Win + X
Disk Management
Right-click the disk number in question
Check properties to ensure the model matches the external you're wanting to set offline
Right-click > Offline

The disk is Online but the option "Offline" don't appears on Right-click menu.

I don't recall you answering the question of what the hardware brand and model is (or I missed it).

I use Lenovo IdeaPad Y510 with Windows 8.1. The external drives are:

Iomega Prestige 1Tb

Seagate Desktop Expansion 3Tb

and can you remove the OTHER drive ?

Thanks all for your suggestions. I've learned several interesting things about Windows. I've discovered a nice software like Process Explorer. It looks like this is a Windows problem without a secure solution. The answer by Michael Best is a practical solution.