Step 1: For This Simple Hack, You Need:
An unwanted floppy drive
Shrink Tube or Electrical Tape
Step 2: Prepare the Connector
Break off the pieces of the board until you are left with only the plastic connector and 4 pins.
Use the soldering gun to assist in cleaning the old solder off of the pins.
Step 3: Prepare the Fan
(Save that molex cable, it could be useful in future hacks!)
Step 4: The Final Touch
Which to remove it up to you, yellow is 12v and red is 5v DC; both blacks are Ground.
I ran mine at 12v and it was too noisy for my taste, so I went with the 5v configuration as shown.
(Note: the pins can be moved from one slot to another in the connector, this isn't a permanent decision.)
Solder the wires to the pins, then shrink tube or tape them to avoid shorting.
Install into your case and enjoy!