MyBook running (sounds like reading/writing data) even when PC is off (OS: Ubuntu 9.10)

I have a 1TB WD MyBook Home Edition external HDD. When the computer is turned off the drive keeps spinning and makes the whirring noises that I associate with data being read or written.

I have another identical 1TB WD MyBook Home Edition which does not do this. The only difference is that the first one (the one that is constantly working) has had the SmartWare disabled as per this post:

I hope someone can help or suggest something.

Many thanks in advance.

P.s. I am running Ubuntu not windows but it should make no difference when the machine is off :slight_smile: