I just happen to be using target disk mode, so I'll jump on this one. It is a way to turn a very expensive computer into a hard drive - temporarily - for diagnostics. It require two firewire capable Macs. Have the 1st computer operating normally, 2nd computer off. Connect the two by firewire. Start #2 and immediately after the chime, press and hold the "T" key till you see a moving firewire symbol appear on its screen. Release the "T" key, and you will see the hard drive (s) of the "target" computer appear as ejectable external drives on #1. You may use them as such - open, close, copy, & delete files, etc. You can also run diagnostics (disk utility, etc) on them. When finished, eject the drive(s) from #1. Then press and hold the power button on #2 until is shuts down. You may then restart it normally. NOTE the "AFTER THE CHIME" when putting a computer into "target" mode. If it don't chime, it won't start in "target" mode. Daniel On Mar 8, 2010, at 3:38 PM, John Gilbert wrote: > You wrote: > > What is target disc mode? > >> Will it start in target disc mode ? >> On Mar 8, 2010, at 10:55 AM, Shane Hartley wrote: