Time to upgrade "from" the Win 7RC.

This article describes the Windows 7 Beta and Windows 7 Release Candidate (RC) expiration dates and their expiration functionality.

http://support.microsoft.com/kb/971767

Windows 7 Team wrote...

While most people who tested Windows 7 have now moved to the final version, some are still running the Release Candidate. If you haven’t moved yet, it’s time to replace the RC.

Starting on March 1, 2010 your PC will begin shutting down every two hours. Your work will not be saved during the shutdown.

The Windows 7 RC will fully expire on June 1, 2010. Your PC running the Windows 7 RC will continue shutting down every two hours and your files won’t be saved during shutdown. In addition, your wallpaper will change to a solid black background with a persistent message on your desktop. You’ll also get periodic notifications that Windows isn’t genuine. That means your PC may no longer be able to obtain optional updates or downloads requiring genuine Windows validation.

To avoid interruption, please reinstall a prior version of Windows or move to Windows 7. In either case, you’ll need to do a custom (clean) install to replace the RC. As with any clean installation, you’ll need to back up your data then reinstall your applications and restore the data.