hey sorry to answer so late but _Sky had some good links there...reformatting a hard drive will not delete the partition it will only move the info to the end of the drive where a person with some puter savvy will find it...the only way to ensure nobody gets the info off these disks is to take a hammer and smash the shite out of them or if you are planning to use them again get a program like paragon's partion magic and do a military format...what this does is securely deletes all info by changing all the 1s to 0s and all the zeros to ones...they do this seven times...hope that helped...