If you are running any of the preview versions of Windows 8, its time to upgrade. Microsoft released Windows 8 first as a Developer preview, followed by Consumer Preview and then Release Preview. All these versions will expire today (Jan-15th), after which you need to upgrade final versions of Windows 8.
You receive the following message on the Activate Windows screen in Control Panel:
The license for this pre-released version of Windows has expired. You’ll need to enter a new product key to activate Windows. Until you activate, Windows will restart every 1 hour, so you should back up your data.
Install the latest version of Windows
•You receive the following message on the Windows Activation screen:
This pre-release version of Windows has expired. Your computer will restart every 2 hours and you might lose any unsaved data.
•You receive the following message on the Personalize pane in Control Panel:
You need to Activate Windows before you can personalize your PC