The CPU 11 of the personal computer 1 controls the CPU 32 of the adaptor 26 made of a semiconductor ID to compute a hash value of a content-managing music data base recorded in the HDD 21 and store it into the nonvolatile memory 34. When playing back a content recorded in the HDD 21, the CPU 11 computes the hash value of the music data base recorded in the HDD 21, compares it with hash values stored cumulatively in the nonvolatile memory 34, and controls the playback of the content from the HDD 21 based on the result of the comparison.