If you ever want to totally get rid all data on a hard drive, the best thing to do is zero-write it. As opposed to formatting, which only erases links to files (which, practically removes everything) but leaves the actual data, zero-writing actually sets the value of each sector of your hard drive to 0. This insures the data is removed as everything is totally overwritten.

Zero-writing a hard drive is always a good idea if you are getting rid of an old hard drive as you know what might happen to it. In order to zero-write a drive, you can download the hard drive tools from your hard drive manufacturer’s we site, or download a copy of the Ultimate Boot CD as it contains the tools for virtually all manufacturers.