Yes…for the 1000th time!
You NEED to overwrite the entire drive with a secure erase within Disk Utility. The only way to make sure data currently on the drive is not recoverable is to overwrite it. And this is what a secure erase does.
On a computer with OS 10.6 installed…a secure erase CANNOT be done without booting the computer from a source other than the internal HD. This is why you need an OS 10.6 install disk. If you had an external USB hard drive with an OS on it that this MacBook can boot from…you could also do a secure erase this way.
The ball is now in your court. Do as you will!
- Nick
p.s. And again. The "clearing & deleting" you mentioned will not get the job done. I explained why earlier.