Unknown device?

I have uninstalled WD SmartWare software (sorry, it’s just horrible), and now I see an “unknown device” in the Device Manager. It also appears when I try to “safely remove” my MyBook Essential 2TB. That’s what I see in the “Safely Remove Hardware” window:

USB Mass Storage Device

  • – WD My Book 1110 USB Device

|      |- Generic volume - (H:)

|- Unknown device

Does anyone know what this “unknown device” is and how to get rid of it? The hard disk is working OK, though most of the time I don’t succeed in “safely removing” it: Windows tells me that some program is using it, although I don’t have any application running.