If you have another Mac available to you, this is a fast way to boot up and get your recovery scan going. This method also provides the ability to verify the files immediately after they are recovered with the programs normally used to access the files. To boot from a second Mac, you will be using what is referred to as FireWire Target Disk Mode. Additionally you can use the secondary Mac as your workspace and to recover your files.
Setting up Target Disk Mode
Turn off the machine with the corrupted hard drive.
Connect both machines using a firewire cable.
Boot the secondary Mac as you do normally.
Boot the machine with the corrupted hard drive, while holding the “T” key.
Hold the “T” key until you see a FireWire icon floating across the screen.
On your secondary Mac install and launch Data Rescue 4.
In Step one of Data Rescue 4, select the Target FireWire connected Hard Drive as the drive to scan and click next.
In Step two choose the proper scan method to start scanning for your files.