How Do I Wipe My Hard Drive Clean?

I need some one to take me step by step "SLOWLY" and tell me how I can wipe my Hard Drive completely Clean, as if it was right out of the box.I am not all that bright when it comes to computers.But come on.How tough can it be, if you are taken through it one step at a time? Please don't use computer Lingo while holding my hand through this. Just tell me as simply as you can, how a computer browser type of person can do this task all by themselves.there has to be some one out there that wants to share the secret?I have a few buddies who do it all the time, and when I ask them how to do it.they just say, that it is to difficult to explain as if it is a Big Dark Secret.I would Love to be able to do it myself.can some body tell me the easiest way to do it?