Here we go; Click shortcut for your operating system (SEE BELOW)
This we take to the drivers page were you can select and download the driver you are looking for (Choose "Driver - Network")
If is onboard ethernet it'll be "INTEL Gigabit" (FOR XP ONLY) or "INTEL PRO/1000 GT" (FOR ALL O/S)
If not onboard (i.e PCI e.t.c) then your choose the driver appropriate to your hardware
BUT I'm sure your looking for the onboard ones anyway.