I’ve had so many clients and friends ask what they need to do to safely give an old Mac to a relative or donate it to charity. The easy way is to use the disks that came with the computer–insert the disk and use the Disk Utility program to perform a secure erase (I recommend the 7-pass erase option, which writes zeros over the entire drive 7 times), and then reinstall system software.

But what happens if you don’t have the disks your computer came with?

A favorite blog site, The Unofficial Apple Weblog (TUAW for short), has a mini tutorial on how you can use your current computer to secure-erase your old one. Here’s the tutorial:

http://www.tuaw.com/2009/04/27/tuaw-tip-clean-your-hard-drive-with-target-disk-mode/

There are two main problems with this solution, that you should be aware of before going this route:

1) It doesn’t work with the newer MacBooks (including the MacBook Air, but not the Pro), as they don’t have a FireWire port. So you can’t do Target Disk mode. If this is your situation, you have two choices: either borrow a friend’s Mac that does have FireWire, or buy the Mac OS X installer (or the OS X Tiger installer will work, if you happen to have that around) and run the Disk Utility program from the installer disk.

2) If you’re giving the computer as a present or a donation, the recipient won’t be able to use it if all you do is do a secure-erase. Because if all you do is erase the drive, there won’t be any Mac operating system on there, and it won’t start up! This is why it’s always good to save the disks that come with your computer when you buy it. To solve this problem the only solution is to install OS X on your old Mac using installer disks.