The invention specifies a navigation or multimedia system in which a check is carried out to determine whether a user of files, such as roadmap data, is authorized to use these files. To this end, the navigation system has means for checking authorized use of files on the bulk storage medium on which the files are stored. The files are stored in encrypted form, in particular. In accordance with an inventive method for enabling the use rights on a file, provision is made for the user to enter a first and a second scrambled code (PIN and ACW) into the navigation system first. These codes are converted into vectors. A device identifier ID of the navigation system and the first scrambled code PIN are first used to calculate a key k. The key k and the second scrambled code ACW are used to calculate an access authorization identifier AC, which is compared with the access authorization identifiers for the files stored on the storage medium. If these identifiers match, the associated file is decrypted and enabled for use by the navigation system.