Shoutbox

i know that Darik's Bute and Nuke is powerful software and can completely delete EVERYTHING on hard drives.
but i was wondering 2 questions from people who may know more about it or have used it ...

1)
Does it completley delete EVERYTING - un tracable? (even by police for instance as they can race some things) but does this stop that from being able to happen?

and

2)
Does it give you the option to nuke just 1 hard drive or does it automatically nuke them all?

thanks for any help