i need to scrub my hard drive

Although I"ve never done it, I've heard it mentioned numerous times on this board before. Just do a reinstall of OSX and select the option the wipes the hard drive clean first.

Make sure you use the utility correctly there are sevral options, there is one that lets you overwrite the HD several times with useless data, however this takes a few hours, so its worth it if your data is gone.

So , you have two threads on the subject. You could download the OS or get it from a friend. Using a magnet to wipe everything is pretty dangerous! It could seriously damage the drive. Goodluck!

ok, if you're just selling the computer and do not care about the os.

boot holding down Command (apple key) + s
this boots into single user mode.

from there you can type
but this is still recoverable, though i have to say, recovering data on an OS X disk after you've reinstalled the operating system is not going to be easy.

but, there is another solution... if you want to zero your drive completely. and i mean COMPLETELY! it will require a low-level format after this... you can run these commands.

at the single user prompt type
and you will be able to see something like /dev/disk1s2 19640808 12730368 6714032 65% /

it's the slash (/) that is important, whichever listing has that is the one you want.

now, type
replacing the ### with what the df command told you for /

good luck covering your kiddie pr0n.