On homes constructed prior to 1962 or so the electrical systems primarily consisted of two-wire branch feeders, containing a hot (ungrounded) conductor and a neutral (grounded) conductor. The receptacles in the home would have originally been two-prong receptacles, lacking a receptor for a grounding prong.
A lot of today’s appliances including TV’s, PC’s, washing machines, toasters, etc. contain a grounding prong as these items require grounding to either be protected from surges, or for safety. So, often times a handyman or homeowner will simply swap the two-prong receptacle out for a three-prong receptacle.
This simple swap out is both an equipment hazard as well as a safety hazard. Without running new wiring with an EGC (equipment grounding conductor, or referred to as “ground”), any appliance utilizing a grounding prong is subject to being damaged due to power surges or lightning strikes. More concerning is the safety hazards associated with appliances plugged into receptacles with “no ground”. Let’s take a washing machine or toaster for example, if an internal wiring fault in these appliances contacted the metallic enclosure of these appliances, and you in turn touch the appliance, YOU are now the path to ground and would be electrocuted.
There are three approved ways to change out a two-prong receptacle.
Simply put a two-prong receptacle back in its place.
Run new wiring from the electrical panel to the receptacle containing a hot, neutral, and ground.
Protecting the receptacle with GFCI protection.
The third option is typically the “easiest” but comes with limitations as well. This option will protect you from a safety standpoint by shutting off power to the receptacle if as little as 5 milliamps of differential is detected between the hot and neutral conductors. But this option will not protect your electrical equipment if a power surge occurs.
If protecting the receptacle with GFCI protection is conducted, there are two ways to go about it. One being protecting the whole circuit with a GFCI breaker in the electrical panel. The second would be GFCI protection at the receptacle itself, the first receptacle on a circuit can contain the GFCI receptacle itself, and each receptacle downstream can be protected if connected load side to the GFCI receptacle. In either case each receptacle would need to be labeled “GFCI Protected” and “No Equipment Ground”.
A little disclaimer, I’m not a licensed electrician, and each situation is different, any electrical work should be conducted by a licensed electrician.