The solution is easy provided you have a metal outlet box. Simply buy a 3-pronged outlet and a package of green ground wires (pre-looped, and with green screws, called 'Equipment Bonding Jumpers'). Remove one of the old two-prongers where you want to install the PC. Install the new grounded outlet to the white/black wires and install the green ground wire to the ground screw of the outlet. At the other end of the green ground wire, screw it to the metal box with the green ground screw. Push the wires back in the box and attach the outlet to the box. You now have a grounded outlet.
Two physical grounds??
Due to construction issues the only way to ground my line conditioner is by instaling a dedicated ground rod for it (i.e. the house outlets are of type that accept a 2 prong plug). This dedicated ground rod for the line conditioner will be about 16 feet away from the ground rod for the electrical wiring for my house. By doing this would I get into trouble regarding a "ground loop".