In the past years, a CNC machine was a very complex machine, the same was when the first 3d printers were released.
However, now it is relatively easy to build one of those two.
Recently i found some tutorials on how to build a mini plotter with two dvd drives, one arduino board, and two L293D motor drivers.
Unfortunately i did not make photos on the building process, but for who is interested here is a detailed tutorial, similar with what i did: http://www.instructables.com/id/Mini-CNC-Plotter-Arduino-Based/
What i did not had, was the servo motor, so my plotter could not lift the pen from the paper. However i don't think that is a problem, because i plan to mount a burning laser instead of a pen, to engrave text or cut slim pieces of plastic.
Here are two videos with the plotter in action:
I am planning on building a big version of this, with NEMA stepper motors.