Shut down all applications that access a removable hard drive. Wait for the termination of calls to it (the led on the device should stop flashing).
If you are using Windows operating system, look in the lower right corner on the taskbar icon with the green arrows zvoma. Click it twice and you will see a list of devices connected to the USB interface. Find in this list a removable hard drive, highlight it and then click "Stop". Wait for notification that the device can now safely removed. Don't stop at the error with another USB device, for example, a Bluetooth keychain, a GPRS or 3G modem, printer.
In the Linux operating system to stop external hard drive in two ways. To use the first of them, look directly on the desktop of the device icon, and then click the right mouse button. On the shortcut menu, select "Disable" or similar. After this, again open the context menu with the right mouse button, and then select "Extract".
To disconnect the external hard drive is an ideal way to open a console and run the command su. Enter the root password. Start the file Manager Midnight Commander mc Directive. Navigate to the mnt folder located in the root folder. If you cannot find your external hard drive, try to find it in the media folder, also located in the root folder.
Enter the umount command with the argument as the name of the external hard disk, for example, umount sda1. Wait till the led will stop blinking - he must go out or light up constantly. Then enter the eject command with the same argument, for example, eject sda1. Now the led should go out, even if it has been glowing, and a removable hard drive should stop the motor.
Now disconnect the external hard drive. If it attaches to two USB ports, disconnect the plugs from both. If it has external power adapter, first pull the latest from the wall outlet and then disconnect the drive from the USB port of the computer.
It happens that the external drive is busy, or another application that cannot close. This, in turn, makes it impossible and stopping the device. Then for safe disconnection will shutdown the OS and wait until the computer turns off.