A transfer file stored in a game cartridge has a transfer file nested structure in which a transfer file in which a game program is converted into a transfer file is further converted into a transfer file. Specifically, the game program is converted into a transfer file at a level "1" (base level) of the nested structure, and a transfer file [n-1] converted at an immediately lower level "n-1" and the game program are converted into a transfer file at a level "n". Note that n=1, 2, . . . N.