I have Virtual PC ver 126.96.36.199 installed. Using loopback adapter. When I start virtaul machine I get an error (Network Adapter with address 00:00:00:00:00:00 failed to initialize because the address is a null address). If I set up network on the virtual machine as shared NAT I can connect to the inerenet. But I can not ping between the two virtual machines. I have my loopback adapter address set at 10.10.10.3/24. On each machine I have the set as 10.10.10.1 and .2 /24 I set the default gateway at 10.10.10.3. I found some older post on the net about editing the registy. Not sure if I would edit the registry on host PC or Virtaul pc's. I am keeping the virtaul machines so they will only talked to each other and not go out to the internet.