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.
The 30 day loophole provided some interesting ways of using Windows 7, including having the upgrade version install over itself and save a great deal of money over buying the full retail version. With the grace period, you could also make temporary installations for quick tests of software compatibility. Those options seem to be gone now with Win 8.
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.
And you can read more on the story at ComputerWorld.
