Simply stated, 3-prong receptacles require 3 separate wires; the black (or red) hot wire, the white neutral wire, and, what is usually a bare wire for the ground. This ground wire is probably what youíre missing, but simply adding it probably will not bring the house up to acceptable modern code requirements. The one little quirk in municipalityís code requirements is that they (the municipality) usually donít require upgrades to electrical systems unless there is a remodel /addition/etc. which requires a permit. Even then, many times only the remodeled portion must be brought to code.
Most houses built after world war II and before 1960 were wired with plastic-insulated wires wrapped in some type of sheathing. This is similar to modern cabling, except they only had 2 wires (black and white), and houses built since then (more or less after 1962) now carry the extra bare ground wire in the sheathing. This ground wire should tie every outlet box, receptacle, switch, or otherwise, to the main circuit panel , and then on to a grounding rod or water pipe. The safety aspect only works if they (the outlets) are all grounded to each other, and to the main circuit panel.
If these pre-1960ís homes were built using steel conduit or armored cable, it is possible that the municipality would allow to use this steel sheathing as the ground providing it all leads back to the main circuit panel. Otherwise, a grounding wire needs to be added, and municipalities may not allow just a bare wire running exposed in all the walls. Adding GFCIís adds a level of protection, but GFCIís only protect items plugged into them. They canít easily protect lighting fixtures or light switches, and many items found in the home could cause the GFCIís to trip just by turning the item on. The ground wire is designed to help protect everything. As an esthetic bonus, the grounding of the outlets helps cut down static in TV and stereo reception.
I wanted to give you this overview even though the type of home I covered probably does not describe yours. If it is a true Victorian, it could have been easily built 100 years ago, in which case the wiring was probably added after the home was built. At any rate, it would fall in the other category; houses built before the war. Whether, the electricity came with the house or was added later, modern wiring knowledge and techniques simply were not known or available. Your house probably has knob-and-tube, a wiring technique where individual wires are strung between glass insulators, called knobs, and through glass tubes. This insulation, before the invention of plastics, probably consists of no more than creosote-soaked cloth wrapped around undersized wire. None of this comes close to modern code, and simply adding 3-prong receptacles, thus allowing modern, larger amperage devices to be plugged into the existing system, is a dangerous, and potentially deadly proposition. Moreover, you still may be using 60 or 100-amp main service with fuses. The reasons that should be replaced Iíll save for another long-winded discussion.
Rewiring an entire house can be pricey, but much of the cost is just for running wire, and that can be a DYI project. Shop around, and you may find an electrician that would be willing to work with you on that. Also, if your house had electricity added after it was built, much if not all of the wiring is simply hidden under baseboards, making the rewire project even easier. You can usually tell if the wiring was added after the home was built, because the outlets are located in somewhat unnatural, inconsistent locations (baseboards, very near door frames, etc.), picked because of their ease of running the wire rather than use practicality.
Now I did not intend to scare you, just inform. Before you go and start ripping walls down to rewire, have a qualified electrician evaluate what you have. It is possible that the home was previously rewired, and some, if not all, of the electrical system can be salvaged. And consult your municipality to see what they require.