I upgraded my ASUS KFN32-D SLI/SAS motherboard to the latest BIOS version and swapped out the 2 dual-core procs with 2 quad core procs. After installing Server 2008 Datacenter onto the system I noticed that it was not connected to the network. I open device manager and see no network adapters. I have to go up to View -> Show hidden devices to even see the virtual WAN Miniport adapters.
This problem happens in Vista and Windows 7 (all x64). What is even stranger is it all works in x86 mode. What in x64 could be causing windows to not even detect hardware that works in x86? Is the boot manager possibly the culprit?
Try downloading and applying the 64-bit NIC drivers from Asus' website.