I am very sorry but the Nero software will have to be supplied by Nero if lost. Windows media player 11 can be used as your server in place of the Nero software. Please see the FAQ link below.
http://support.dlink.com/faq/view.asp?prod_id=2692&question=DSM-120%20/%20DSM-320%20/%20DSM-320RD%20/%20DSM-510%20/%20DSM-520%20/%20DSM-750