You should have Hyper-V for running Emulator in Windows 8. Hyper-v is virtualization solution.You can install this by,
Control Panel >> Programs and Features >> on the left panel Click on “Turn Windows features on or off”. Select “Hyper-V” option and Click on OK.
To fix this spefic issue, Open the Hyper-V Manager from the start menu, and open the Virtual Switch Manager. Remove any existing switches, and try make a new virtual switch with a connection type set to internal.
You might need to run XdeCleanup.exe afterwards Restarting the machine also will help