Microsoft recently released its new operating system called Windows 8 Release Preview.So,if you have already downloaded Windows 8 RP ISO and trying to install it from a bootable CD or USB then it will ask for product key.
Update 1: All the windows 8 Version Keys works only till January 16th 2013.After that you will get notification asking to buy full version of windows.If you don't upgrade then your pc will restart for every hour.The only way to fix
