One of the kids put a DRIVELOCK password on one of the hard drive laptops in our Ubuntu LAB. I tried removing the drive and reformatting it via USB to make it usable, but it doesn't even show up as a drive or partition. However it does show up as /dev/sr0 however it says there is no media detected when you try to do something to it.
If the drive is password protected, you can not format or use killdisk. The firmware will not permit any access. Depending on the brand of hdd you might want to call the manufacture, and see if they can help you, or you can try HDD Wipe Tool. Unfortunately its only available for windows, and can be downloaded here
You could also try booting from a Live CD like Ubuntu, and run the command below. Make sure you choose the right drive.