The only way I know of to erase all sectors, even those not exposed to the data interface at all (not only hidden data sectors) is using something like this hardware
. This will brick the drive and render it unusable!
If you are looking for a non-destructive software solution it would have to be specific for every situation (how and where the data is hidden and on what kind of drive).--
Got some spare cpu cycles ? Join Team Helix or Team Starfire!