It is possible for an information processing device to read or write a large amount of contents-related information more quickly if the device has a relatively small processing capacity. The file format identifier information and the block identifier information that correspond to contents-related information are identified in Step S11 and it is determined in Step S17 if the file format version information read out from the file identified by the file format identifier information and the predefined file format version information agree with each other or not. If it is determined that the two pieces of file format version information agree with each other, the related information is read out from the block identified by the block identifier information of the identified file according to the block position information of the identified file in Step S22.