That's an EIDE drive so at least we don't have to worry about SATA power!
Funny how people get my name wrong every time!
I'll try to explain again,
You have two options:
1. If you have a single power source (you said 19V originally) it will have two output wires. One is 0V (ground and is sometimes called the negative wire) and one is +19V. You can connect the ground directly to the middle two pins on the drive power connector. You then have to regulate +19V down to +12V and connect it to the +12V input on the drive power connector AND you have to regulate +19V (the same one) down to +5V and connect it to the +5V input on the drive power connector. Two regulators are needed.
2. You have two different power sources, one produces 5V and the other 12V. Each has two output wires, one supply has 0V and +5V, the other supply has 0V and +12V.
Connect the ground (0V) from each supply to the ground on the drive, you can use either of the middle pins on the power connector, they are linked together inside the drive anyway. The +5V wire from the 5V supply goes to the +5V input pin on the drive and the +12V from the 12V supply goes to the 12V input on the drive.
The two voltages are not alternatives, they must both be present for the drive to work. Usually, the 5V runs the control circuits interface while the 12V runs the spindle and radial motors and the laser.
Brian.