I had very similar issues with an HP 9300 workstation and found the only solution for that was to switch on detect PNP devices. I had exhausted most of the other techniques for getting the drivers in and then found a post mentioning the the Nforce 5 nics require 2 drivers. One for the machine to recgonise the nic and the other as the driver for the nic. I was using MS WinPE created from a win2003 server. It may be worth a try if you havent already