|There must be a continuous ground connection between the computer's power supply and the source of the AC power it's plugged into, all the way back to the power panel the AC circuit is connected to. E.g. there must be 3 prongs on the AC end of the cord that plugs into the power supply, if you have the power supply's cord plugged into a power bar or a UPS, that device must have 3 prongs on it's power cord on the AC end, and the AC receptacle (wall "plug in"; "duplex" if there's two) on the wall must have a ground connection all the way back to the power panel. |
If you're not sure whether the AC receptacle is grounded, you can buy an inexpensive device you plug into it that will show you whether it's wired properly by means of leds or neon bulbs lighting up on it,
or - if you're careful and you have a voltmeter, you will see, if nothing's wrong, when you plug the meter's leads into the receptacle that you get the line voltage between the two live connections, and between one of the two live connections and the ground connection; if measuring between either live connection and the ground connection BOTH show no voltage, the ground connection is not connected at the receptacle, or the ground connection is not connected somewhere in the wiring between the receptacle and the power panel.