The discs for your MBP are model-specific. You can't boot a different computer with them.
Hook up a firewire cable between the two Macs and boot his MB in Target Disc Mode.
It will appear onyour MBP desktop as an external disc.
Use DU from the MBP to repair the MB HD.
Disconnect all other FireWire devices from both computers before you use FireWire target disk mode. Do not connect any FireWire devices until after you have disconnected the two computers from each other or have stopped using target disk mode.
To use FireWire target disk mode
1. Make sure that the target computer is turned off.
2. If you are using an Apple portable computer such as a PowerBook or MacBook as the target computer, plug in its AC power adapter.
3. Use a FireWire cable to connect the target computer to a host computer. The host computer can be powered on.
4. Start up the target computer and immediately press and hold down the T key until the FireWire icon appears. The hard disk of the target computer should become available to the host computer and will likely appear on desktop. (If the target computer is running Mac OS X v10.4 Tiger, you can also open System Preferences, choose Startup Disk, and click Target Disk Mode. Restart the computer and it will start up in Target Disk Mode.)
5. When you are finished repairing his drive, locate the target computer's hard disk icon on the desktop of the host computer and drag it to the Trash or choose Eject (or Put Away) from the File menu.
6. Press the target computer's power button to turn it off.
7. Unplug the FireWire cable.
(extract from http://support.apple.com/kb/HT1661)
Should it prove necessary, you can also retrieve data from the target HD to your Mac or to another external drive (but use a USB one while in TGM)
