No writable partitions found

Welcome to the Community. 

This error message seems to be related to WD SmartWare as opposed to the WD My Book Essential itself. This message is the result of the application being unable to properly use your hard drive because it is not detected, it’s locked, or needs to be formatted/partitioned.

I would recommend ensuring you can see the actual WD My Book in the Computer section of Windows Explorer. If you can then try to manually copy a file into it. If it accepts the file then the next step would be to uninstall WD SmartWare and install an updated version from the following link:

http://www.wdc.com/wdproducts/wdsmartwareupdate/wdsmartware.asp?id=wdfMB30_Essential&os=win

If that does not work then you may have to format (Erase) your hard drive:

http://wdc.custhelp.com/app/answers/detail/a_id/3865/

Regards,