WD TV Live streaming media player external HDD won't turn off?

I have 2 WD TV Live media players 1 x Live streaming unit and 1 x HD unit.

When both media players are switched off and I plug in my portable HDD to the WDTV Streaming player - the HDD runs and won’t turn off. When I plug the portable HDD into the WDTV HD media player it stays off until I turn on the media player which is correct.

Both media players have the latest updated firmware.

Does anyone have any idea on how to prevent my portable HDD from continually running with the WDTV Streaming media player in the powered off state?

Your SMP probably isn’t OFF, it’s in STANDBY, which still allows network access to the USB disk, hence why it’s powered on.  

If you want to turn your SMP COMPLETELY off, so that the HD goes off as well, hold the power button down for 3 seconds.

Thanks for your help.