Insert your OS X install disc and reboot your machine while holding down the "C" key. It will walk you through all the necessary steps...you'll want to "Erase and Install."
Insert your OS X install disc and reboot your machine while holding down the "C" key. It will walk you through all the necessary steps...you'll want to "Erase and Install."
Sorry, I haven't done an Erase and Install in a long time, so I'm going from memory here. I think there's an option somewhere in the process for you to specify overwriting all the data on the disc. If not, you can open Disk Utility while booted from the disc and explicitly erase the hard drive that way first. The number of passes you do is up to you...35-pass is overkill and will likely take multiple days to complete.