If your network adapter has an onboard processor, designed to offload processing from the CPU, Windows 2000 won't use this capability, even if your NIC driver supports it.
To enable support for network adapter task offloading, use Regedt32 to navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
On the Edit menu, Add Value name DisableTaskOffload and set the data type to REG_DWORD. In the DWORD Editor, set the data value to 0.