since they make hundreds if not thousands of variations of network cards, asking for "lan" driver is pretty vague. provide the make and model of your pc or if its cusom built the motherboard make and model.
Go to ur motherboard manufacturers site. U just cant download lan / network card driver and install it. It wont work. Now a days network card components r integrated on the motherboard itself. If for some reasons u cant find ur driver, buy a network card and install that into ur PCI slot of ur motherboard. They r very cheap.