In the U.S. those three-pronged plugs are referred to a "grounded." You want the ground (not to be confused with the past tense of "grind") to be plugged in, not by-passed with those orange adaptors that used to be sold readily in hardware stores (idea being you would use the screw from the wallplate with a little tab on the adaptor and provide an alternate ground). If you can get a power supply (which doesn't actually supply power, but simply manages all of the plugs in one place, and everything can be turned off with a master switch) you'll save your computer and periferals the damage of an energy surge.

That's about all I know about electricity in a nutshell.

SRS