On a recording medium, there are recorded content files and an index file. The index file is constituted by attribute information of the content files (title text data, thumbnail-image data or the like). In the case of changing (recording or deleting) the content file, the index file is updated after the change. A computer sets up, in a nonvolatile memory, status information indicative of being in a predetermined process stage, during the predetermined process stage from a start of changing the content file to a termination of updating the index file. The computer, at turning on power, determines the matching/mismatching between the content and index files recorded on the recording medium utilizing the status information, thus repairing the index file as required.