A control apparatus system comprising: a recording medium storing: additional software comprising software identification information; recording medium identification information; and encrypted information generated by encrypting the software identification information, using the recording medium identification information as a key; and a control apparatus which is used with the recording medium connected to the control apparatus, the control apparatus comprising: a storage; and a controller which can access the recording medium and the storage, the controller being capable of performing the steps of: obtaining the encrypted information from the recording medium; obtaining the recording medium identification information from the recording medium; obtaining decrypted software identification information by decrypting the encrypted information, using the recording medium identification information as a key; obtaining the software identification information from the additional software; comparing the decrypted software identification information and the software identification information obtained from the additional software; and; storing the additional software in the storage when the decrypted software identification information agrees with the software identification information obtained from the additional software as a result of the comparison between them, and wherein an area which is in the recording medium and which stores the encrypted information is a protected area configured with a file system which can be read by an OS of the control apparatus. a recording medium storing: additional software comprising software identification information; recording medium identification information; and encrypted information generated by encrypting the software identification information, using the recording medium identification information as a key; and a control apparatus which is used with the recording medium connected to the control apparatus, the control apparatus comprising: a storage; and a controller which can access the recording medium and the storage, the controller being capable of performing the steps of: obtaining the encrypted information from the recording medium; obtaining the recording medium identification information from the recording medium; obtaining decrypted software identification information by decrypting the encrypted information, using the recording medium identification information as a key; obtaining the software identification information from the additional software; comparing the decrypted software identification information and the software identification information obtained from the additional software; and; storing the additional software in the storage when the decrypted software identification information agrees with the software identification information obtained from the additional software as a result of the comparison between them, and a storage; and a controller which can access the recording medium and the storage, the controller being capable of performing the steps of: obtaining the encrypted information from the recording medium; obtaining the recording medium identification information from the recording medium; obtaining decrypted software identification information by decrypting the encrypted information, using the recording medium identification information as a key; obtaining the software identification information from the additional software; comparing the decrypted software identification information and the software identification information obtained from the additional software; and; storing the additional software in the storage when the decrypted software identification information agrees with the software identification information obtained from the additional software as a result of the comparison between them, and obtaining the encrypted information from the recording medium; obtaining the recording medium identification information from the recording medium; obtaining decrypted software identification information by decrypting the encrypted information, using the recording medium identification information as a key; obtaining the software identification information from the additional software; comparing the decrypted software identification information and the software identification information obtained from the additional software; and; storing the additional software in the storage when the decrypted software identification information agrees with the software identification information obtained from the additional software as a result of the comparison between them, and wherein an area which is in the recording medium and which stores the encrypted information is a protected area configured with a file system which can be read by an OS of the control apparatus.