1. A data accessing method comprising the steps of: obtaining a track information entry about a predetermined track from a play order table having a plurality of track information entries, the track information entry pointing to a track descriptor in a track information table; obtaining the track descriptor from the track information table, the track descriptor including a decryption key corresponding to the predetermined track, pointer information that points to a part descriptor of a plurality of part descriptors in a part information table, and name pointer information that points to a name slot entry in a name table having a plurality of name slot entries; reading the name slot entry that corresponds to the name pointer information in the track descriptor; reading the part descriptor that corresponds to said pointer information in said track descriptor; and reading a part of an audio file according to part pointer information in said part descriptor, said part pointer information pointing to at least a part of a file.