Start on the first boot to the desktop after the upgrade to W8.1. It reported it could NOT connect to a network. Once I got to the desktop I opened the NETWORK AND SHARING CENTER and DISABLED and ENABLED my NIC. That made the connection. All was OK for a boot or two after that. However, on a cold boot it is a 50/50 chance that it will not see the cable connected. I've tried UNINSTALLING the NIC (RealTek PCIe GBE Family Controller) and re-installing. Again, a 50/50 chance it works on boot. I then went to the RealTek site and noticed they had a later driver with W8.1 listed. Got the driver, uninstalled the old one and installed. No change, same problem? Suggestions? Irv S.