http://www.computerworld.com/s/article/9230399/Microsoft_ends_activation_grace_period_with_Windows_8
http://www.myce.com/news/windows-8-will-not-allow-a-30-days-grace-period-for-activation-63386/
Windows 8 will not allow a 30 days grace period for activation
Microsoft has removed the 30 day grace period for installations in Windows 8. Previously, in Windows 7, customers were given this period of time to provide a legitimate product key and register the operating system. With Windows 8, everyone installing the operating system must enter a 25 character key, else the installation process will stop
If the computer is connected to the internet during installation, Windows 8 will automatically check the key and confirm its authenticity. There doesn’t seem to be any information available yet for those computers that aren’t connected. Only those using a systems builder version or upgrade version of Win 8 will be affected. Computers made by OEM’s like Dell and HP will come pre-activated.
At least one site has already listed some instructions on how to get around this need for a key during installation. You can see their fix here.
http://www.windowsvalley.com/install-windows-8-without-product-key/