I am not sure if you are aware about the PC power supplies and I defenitley do not know what mecca is - except that it is a Holy place.

For your information : In a PC mother board all the different voltages are referred to the Ground plane which also happens to be the SMPS common and which also links to the PC chassis AND the Earth pin in the power socket. This is the most used configuration and the one I have. Maybe there are other methods.

And thus the 5th pin in the sub-D DOES get connected to the ground plane. Nothing to do with the casing of the connector.

Raghu