The two-pronged electrical outlets are old wiring outlets with no grounding when they are installed. In case of a lightning strike, the 2- prong cheater means a prong surge protector is useless as there is no ground prong available to shun the surge off. Whether or not the electrical appliances in your house will get ruined depends on the direction in which the power surge will go in your home's electrical wiring. It is possible to fit in a three-prong into the same outlets without thinking of the cost of rewiring your house as long as the box itself is grounded to make it up to code. To make your two-prong electrical outlets up to code, they need to be replaced. You can call an electrician for consultation, and they can help with the upgrade. You don’t need to go for a full household wiring before you can get it upgraded. You can replace the electrical outlets with newer and safer ones that are up to the current electrical codes. If you are comfortable working with electricity,...