Abstract: Hierarchically organized graphical representations of items and groups of the items of digital information which are available to be ordered by a user are displayed. The user interactively explores the representations and selects items or groups to be ordered, using a pointer. While the graphical representations are being displayed, a list of items or groups which have been selected for inclusion in an order is also displayed. Software is executed which automatically determines the configuration of the computer, and matches the configuration with the stored configuration information prior to the user placing an order. A user may automatically be given access to items in a later revision of the medium if the user had access to the items in an earlier revision.