According to Microsoft, pre-Beta development milestones of Windows 7 fail to play nice with USB network adapters that rely on pre-Windows Vista drivers. The symptoms involve NDIS 5.x USB network adapters not being displayed in the Windows 7 Performance Monitor.
“Perfmon only shows adapters that indicate that they have a physical, hardware connector. Windows Vista and Windows Server 2008 introduced a new Network Driver Interface Specification (NDIS) known as NDIS version 6. Network driver developers are encouraged to move their drivers to this new specification,” Microsoft revealed.