LEFT click the Safely Remove Hardware icon, little green arrow, in the system tray (bottom right of your screen).
OR
You can restart the computer and remove your drive while it is restarting.
It is strongly recommended that you follow one of the above steps as removing a USB device from a computer without doing so may result in loss of information/data.
See also -
Is the internet filtered?Information on the internet filtering in place on our PCs and wifi.