I have a drive I'm going to give to a friend since I got a new one and he wants to expand his storage, but mine has sensitive stuff on it (school docs, passwords, and so on). I already backed it up, but I don't know of any free drive wiping software. I know for a fact you can still recover bits and pieces of data, even with the Windows tool, as I've tried it. If I remember right, zero-filling the drive is the most secure way. So what is a free program that can do this?