Currently Being ModeratedNov 25, 2011 5:59 PM (in response to sue252)
See Mac OS X: How to zero all data on a disk
If you are going to sell the Mac, reload the system software & sell it with the software/restore discs.
Cheers, Tom G4 1.25HGz MDD, PB 12" G4 1.5GHz, Mac OS X (10.5.8), (10.4.11, 9.2.2) iSight,iPad2
Currently Being ModeratedNov 25, 2011 6:07 PM (in response to sue252)
The most effective way is to boot from the install disk, launch Disk Utility, select the drive (manufacturer ID) in the sidebar, select the Erase tab, and click Erase. If you want to do a secure erase the choose security options and do a multiple pass. 7 or 8 passes will be enough. Then launch the installer and install the software. When the setup assistant comes up, shut down. When the new user starts up the computer the setup assistant will come up and the new user can setup a new account. For more detailed directions, please post back.
Currently Being ModeratedNov 26, 2011 11:30 AM (in response to Michael Wasley)
You probably missed this:
If you want to do a secure erase then choose security options and do a multiple pass.
For greater security the data must be overwritten more than once.
Currently Being ModeratedNov 26, 2011 2:11 PM (in response to cornelius)
Probably, but I didn't miss Apple's advice on erasing HDs in Leopard which regards a single pass zero as providing 'good security'. It also points out that a seven pass zero in DU conforms to US DoD 5220.22-M specification; that would appear to be overkill for the average Mac user.
I also came across this at some time which claims that "The 7-pass and 35-pass options are unnecessary for normal users and extremely lengthy; only the CIA, NSA, etc. can recover much, if anything, after 1 pass".
Of course it all depends on how important the security of your data is (patients' medical records, state secrets etc obviously need more care). It will also depend on the level of your paranoia/guilt.