Hyper-V Program Manager
Just a small note to say that here is an interesting article written by one of the virtual machine MVPs on using loopback adapters to communicate between the host and virtual machine environments when a network connection is not available: http://www.devx.com/enterprise/Article/33644
I use loopback adapters all the time within my test environment. I basically setup a single server using routing and remote access to service all of my machines running in vitual and with a link to the outside world using NAT. This configurations allows my virtul network to run even if I don't have a network connection or if it's changing a lot in terms of DNS. I have setup some very nice networks with this including multi-site active directory implementations. One thing about loopbacks being configured it may/could cause slowdowns with certain applications that look for network responses.