Refer: www.tipandtrick.net
To fix the Shared Network (NAT) Internet no connection or not working issue, the resolution is to manually assign the IP address for the DNS Server for the guest operating system to 192.168.131.254, the virtual gateway IP address used by Virtual PC. To make the change (in guest operating system), open Network Connections folder (in Windows Vista, access via Network and Sharing Center), and right click Local Area Connection network icon to select its Properties. Then double click on Internet Protocl (TCP/IP) under General tab or Internet Protocol Version 4 (TCP/IPv4) under Networking (for Windows Vista) tab.
