Electric equipment, and a method and a program for preventing the unauthorized use of same, by which it is possible to prevent the theft of electric equipment installed in an environment where the electric equipment is available for the use of an unspecified number of users and the stealing of information stored in the electric equipment. The electric equipment comprises: an operation limiting section for setting a function limit to make at least part of functions of the electric equipment unavailable; an I/F for connecting an external device to the electric equipment; an external device information obtaining section for obtaining device identification information from an external device connected via the interface to the electric equipment to identify the device; a write control section for associating the function limit with the device identification information of a prescribed external device to thereby obtain a cryptographic key; an NVRAM for storing the cryptographic key; and a comparator for determining whether or not the device identification information obtained from an external device connected via the interface to the electric equipment matches the cryptographic key stored in the NVRAM. The operation limiting section cancels the function limit when the comparator determines that the obtained information matches the cryptographic key.