Do it yourself

Unless a residence is wired either using BX which is armored cable or conduit there is usually no bond available at the box for the ground connection. I'm not sure that two prong outlets are even available so it is usually necessary to use grounded outlets when replacing old worn out units. This then gives you a grounded outlet which is in fact not grounded. Some are tempted to connect the bond or ground to the neutral but this should not be done since the neutral is a current carrying conductor and as such should not be used for the bond. If there is no bond available some GFCI's will not operate properly unless it can be installed as the first receptacle in the string and have a bond carried from the main box to it. Of course you would need to know how the house was wired and in which order the receptacles were connected to one another. This can be determined but is a bit of a pain and then there is the problem of getting a wire to the receptacle. The usual home owner solution is to install new receptacles where needed and let the Devil take the risk. Three prong un-grounded receptacles are no more dangerous than the two prong that were originally in place, its just that they are deceptive. The kitchen and bath are the areas of greatest electrical hazard and if someone is really concerned these areas probably should be rewired. Dale