Today I needed to connect via network to a Virtual PC instance that I had locally, but as I was working offline (with no network cable connected) windows disabled my network interface.
Windows IP Configuration
Ethernet adapter Local Area Connection:
Media State . . . . . . . . . . . : Media disconnected
I surfed around and found some help on this article "Keep Your Virtual Machines and Hosts Talking Without a TCP/IP Connection".
Basicly I had to install Microsoft Loopback Adapter in Vista and after that I was able to manually configure my IP's in order to communicate with the VPC instance without beeing connected and without having my network DHCP server :)