wiping out my data, permanently

[Satcomer]

Well because Disk Utility can not erase the drive it sits on.

[zoranb]

Isnt free space erasing enough? Why must i erase everything? I will first make an secure empty trash to the files i dont want to get their hands on, and then just erase the free space with 35 or so passes!

[DeltaMac]

Originally Posted by zoranb

... What is the best way to make data i have on my power book to not be recoverable?

You asked for the best way - A full erase is the best way. A 35-way erase takes a LONG time. I wouldn't consider that useful for other than the severely paranoid (or a guv'mint agency, eh?)
Boot to your restore disk, and erase the drive with Disk Utility, (choosing to write zeroes if you wish), then continue on with a full restore of the original software. It's not too challenging, and the buyer gets a fresh system (without any of your leftover 'junk')
Completely restoring the system to an erased hard drive does enough writing to the drive, making potential recovery of any erased files extremely unlikely.
Why mess around with a partial job? Did you forget about that folder of personal stuff that you accidentally moved to your Applications folder?
Do an erase and restore - why mess around with partial measures?