NIC MAC spoofing for Cable on your Netwo

Has anyone successfully “spoofed” the MAC address of their NIC (or Hub) in order that all clients on their Win2K network may have broadband access? This particular provider (rhymes with @ gnome) attempts to bind the MAC address of a single NIC and broadband access completely freezes if one attempts to use NAT or attempts to use the MAC address of the hub for verification….any ideas?