Microsoft this week began warning users of the Release Candidate (RC) version of Windows 7 that the free preview version of its latest OS will begin winding down soon. As part of this process, the Windows 7 RC will begin alerting users of the expiration in about two weeks, on February 15. Then, starting March 1, the Windows 7 RC will begin automatically shutting down once every two hours. The RC formally expires June 1, 2010.
To avoid data loss, Microsoft suggests making plans to move to the final, released version of Windows 7 before the automatic shutdowns start. These shutdowns are automatic and come without warning, and any unsaved work will be lost. (Microsoft also notes that pre-release versions of Windows 7, like the RC, are unsupported.)
Between March 1 and June 1, the automatic shutdowns will continue every two hours. But starting on June 1, any running copy of Windows 7 will marked as "Not Genuine" and will exhibit the same behavior as an unactivated version of Windows 7. That is, it will change the desktop background to a solid black color and periodically pop-up anti-piracy messages.
Microsoft does not provide a supported way to upgrade from the Windows 7 RC to the final, shipping version of Windows 7, so customers using the RC will generally have to back up their data and perform a clean install. That said, there are workarounds to this issue and customers who wish to perform an in-place upgrade from the RC to the final version of Windows 7 can do so using the same instructions that allowed upgrades from the Windows 7 Beta to the RC. Those instructions can be found on the SuperSite Blog.
Note, however, that I do not recommend doing this. You will obtain a more reliable system by performing a clean install of Windows 7