Windows 7 RC was released for public use last year.
It enabled the users to check out the Windows 7 operating system by using it as one of their primary operating systems.
It was made available for free.
The free party is over now. As originally announced, Windows 7 RC is set to expire soon enough.
Starting February 15, users on Windows 7 RC would start receiving alerts about the expiry. From March 1, the system would automatically start shutting down every two hours.
After June 1, the wallpaper would be removed. And the system would display “This copy of Windows is not genuine” .
Microsoft is suggesting that users make a decision before March 1. Upgrade to Windows 7 retail edition or switch back to Windows XP or Windows Vista.
Source