hard drive help

[PokerGoblin]

OK

I want to back up my important files and then 'flash' (I think that's the correct term) my hard drive. By that I mean I want to make the computer the way it was when I first pulled it out of the box.

I actually want to erase everything, then 'zero' it out. I believe this is a process of deleting everything, then writing random data over the whole drive, then deleting that and starting fresh, so old data cannot be retrieved.

What is the best way to accomplish this?

PG