The emulator is not yet supported on Win 8.
Whatever you do, DO NOT try to run the emulator with administrative privileges or you will see how incompatible emualtor is, as you will see the new "chic" look of Windows 8 Blue screen of death.
There is a specific problem with the virtual host used to run the emulator, as other virtual solutions can still work like Virtual Box. You can start emualtor in a limited way using Virtualbox on a Win 8 machine, but you will not have access to the toolbar or it will be able to start XNA
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