sometimes people are worried that the information inside a computer will be stolen when the computer is thrown away. for example, if you have a product design on an old computer, somebody might copy your design. big companies have a lot of computers, with a lot of private information on them. they will often pay other companies to remove all the information from a computer before it is thrown away. this usually involves physically destroying the drive. it is possible to non-destructively erase the data on a hard drive by overwriting the entire drive with random numbers. with this method, only the data is destroyed, not the drive itself. this allows the drive to be reused.