Connect the two using a firewire cable.
Startup the new iMac.
Startup the old machine while pressing and holding the T key (on that machine).
This starts the machine in Target mode. If it's cracked monitor is still working, you'll eventually see the firewire symbol on the screen.
In the finder on the new machine, you will see the target machine mount as a firewire disk.
You may open this disk and transfer any files you want on the new iMac.
To erase the old machines, launch Disk Utility (from the Applications > Utilities folder on the new machine) select the old machine's HD (the actual disk, not just the 'Mac HD' volume on that disk, then choose Erase. Disk Utility will offer choices at that point. The 'seven pass' option should be sufficient to your needs.
The seven pass erase takes a few hours. You may want to make this an overnight task for your machine.
Regards,
Barry
