The D-Link ADSL2/2+ Ethernet/USB Modem-DSL-2320B Software is a necessary installation software designed for D-Link modems. It is specifically formatted for USB connections, allowing users to easily install and access the modem's features and settings. By using this software, users can ensure compatibility and optimal performance with their D-Link modem, making it a convenient tool for those looking to set up and configure their internet connection.