Windows 8 is the upcoming version of Microsoft Windows that follows Windows 7. It features a new Metro-style interface that is designed for touchscreen input. When installing Windows 8 you been ask to provide the serial number.
For convenient you find below the official keys which were required to enter while you are using the Refresh and Reset features in Windows 8.
For those who are using the Developer version of Windows 8, they can use the following key
Download Windows 8 Consumer Preview here