Windows 8 sports two very different user interfaces cohabitating in harmony and complementing each other, each one designed for a specific scenario. But the world needs to think of Windows 8’s next generation UI as “more equal” than the older interface.
Offering users both the Metro UI designed for emerging form factors, and a more traditional UI set up to still allow users to leverage more traditional PCs which put GUI and not NUI at the center of the user experience, is the software giant’s way of not compromising.
Metro-only Windows 8 Means the Desktop Won’t Be Loaded at All - Softpedia