A method and apparatus for write protecting a storage medium of a gaming machine is disclosed. The storage medium, which is preferably a removable compact flash memory, contains critical game data for operating the gaming machine. The storage medium includes a data register capable of receiving external data when at least one load condition of the data register is enabled. In the method and apparatus, an address of the storage medium selected by an external device is decoded. If the selected address matches an address of the data register, the load condition of the data register is disabled to thereby prevent writing to the data register.