I have a number of virtual machines running on a very stable Hyper-V 2008 R2 machine. Yesterday’s reboot of my instances to accomodate Windows Update left only my 64-bit Windows 7 instance without a network connection. No amount of fiddling within the instance could restore it. After much frustration I finally removed the Network Adapter from the shut down instance in the Hyper-V Manager and added a new network interface. Upon booting the instance, it installed new drivers and successfully connected to the network.