Microsoft just released Virtual PC 2007, which brings full support for Windows Vista as a guest and host operating system. If you have a wired and wireless connection in your computer, you might find that Virtual PC has ignored the wireless card during setup, but complains loudly about not being able to use that connection when you run a virtual machine.
To solve this problem, get to the network connection properties. In Vista, you can right-click on the network icon in the notification area, select Network and Sharing Center, then select Manage Network Connections. In the window that appears, find your wireless network connection, right-click on it, then choose properties. Check the box labeled Virtual Machine Network Services, and click OK: