Hard drive security

[myuserid08]

I've just sold my old macbook, its got a 250gb hard drive. I have just zeroed out the data, are re-installed tiger and just about to do the same again.
I take it thats enough to completely erase my data?

[NC MacGuy]

If you didn't do a secure delete and reformat, no. Any data not written over by newly installed software can be recovered.

Is that what you mean by zeroing out data?

[velocityg4]

Though that would not meet US Department of Defense standards for cleaning top secret information it is sufficient to stop most anyone from reading your data. To clean it to acceptable standards you would need to degauss it or incinerate. (Entries A,B and M (http://it.ouhsc.edu/policies/documents/infosecurity/DoD_5220.pdf))

Unless this computer is being shipped from Los Alamos Laboratories or was used to store bank, social security and other personal identity that is worth millions anyone who could retrieve and rebuild the information would not bother.

[myuserid08]

During the install process I went to the disk until program > security options > zero out data which I have now done twice.
The macbook was used to hold my clients private and confidential data, just want to make sure its extremely improbable that someone will try and recover the files. Thanks.