The point of this project was to make an office desk fan from discarded electronics. It's a good project for a beginner because it's simple, inexpensive, and useful. The fan is a 120mm 12V DC fan from a broken apple pc. The power adapter, switch, regulator, heat sink (not pictured), and capacitors were all taken from broken electronics and mounted on a scrap of proto board as a simple 12V DC power supply. I used the fan's screw holes as anchor points for some fine wire to attach the proto board. I've used this prototype version regularly to prevent brain meltdown for several years now. The only speed control this version has is a little blue temperature sensor in the air flow. It automatically increases the speed when the air temp increases but you can put a thumb on it to manually increase the speed.
Recently my mom asked for one so I had the chance to make some improvements on the second version. I used a Single Output Supply board as the 12V power supply and a PWM Power Supply board to provide PWM speed control. These two boards were wired together and attached to the side of the fan. Speed can be varied between stopped and full speed by turning the potentiometer knob.