Windows Explorer Ribbon UI
The biggest and probably the riskiest change would be in Windows Explorer. Apparently Microsoft plans to implement the Ribbon UI found in MS Office 2007 and Office 2010 (also in Paint or Wordpad in Window 7) for Windows Explorer.
Windows 8 Windows Explorer
Windows 8 Windows Explorer Ribbon UI (Click to enlarge)
Windows 8 Windows Explorer Ribbon UI Menu
Windows 8 Libraries > Pictures
Windows 8 Libraries > Pictures
Windows 8 System Reset
The Windows 8 System Reset would remove all the installed software and restore default Windows settings.
Windows 8 System Reset
Windows 8 Windows Recovery