According to Broadcom's website, the proper drivers should be on the server 2003's install CD.
http://www.broadcom.com/support/ethernet_nic/faq_drivers.php#15But there are specific drivers listed for server 2003 IA64 and x86-64/EM64T, also -
http://www.broadcom.com/support/ethernet_nic/netxtreme_server.php