Low level formatting needs to be done on 100’s of Hard disks

Low level formatting needs to be done on 100 pictures of hard drives. What's the easiest way?
We are in the process of sending a few 100 hard drives to Delhi office. To be sure of the data security, we need to format all, including the ones using our company content.
We just upgraded our machines with 500 GB HDD and the old ones are needed to be sent to the head office.
Can anyone help us find out the easiest ways that we can try?
