I also add the freecad file in case anyone wants to make modifications or corrections. The model is designed with version 1.0 RC2. In the previous stable version (0.21) of freecad it may give some errors.
The author remixed this model.
I've added the essential elements for building a computer (RAM and SSD) as well as the position of the power button to make it easier to build the case (and know where to place the ON/OFF button).
In the images you can see how it is placed in one of the models uploaded out of the box.