Install and run AIDA32 from the link below to get a report of your computer. On this report you will be able to page down to the modem and it will identify the chipset and even possibly give you a driver link. You can use this then to get the generic driver for the chipset model at the second link.
http://www.aida32.hu/aida32.php
http://members.cnx.net/reboot/