Look in the VBox program settings for the guest and then the network. Under there you will see 3 areas that are able to be changed. The last should be called named. There you should see your Host NIC and should be able to select it. Now for the Virtual adapter that is presented to Windows 7 RC you should select the Inter PRO/1000 MT. NAT if you just want to get to the Internet and Bridged if you need it to function as a network enabled PC as well.