If you want to upgrade to Windows 7 beta to Windows 7  RC RTM, you must immediately do it because as the of Windows 7 beta  to 01 July 2009 Windows 7 beta has begun hourly shutdown and expiry date on 1 August 2009 whereas RC is running Windows 7 on June 2010.How immediately makes you want to upgrade the Windows 7 beta?  just a few steps you need to do to upgrade to windows 7 beta to windows 7  rtm.The first step Attach the Windows 7 RTM Build 7600 ISO, and extract contents to any folder or USB drive, and then Sources in the folder of Windows 7 and open “cversion.ini” file in Notepad and do change the “MinClient” build number to a value lower than the installed Windows 7 build. For example, change from 7233 to 7000, if you have Windows 7 Beta Build installed (MinClient = 7000.0 and 7100.0 = MinServer ).and the last Save the updated file to the same location and run setup.exe for Windows 7 RC but the upgrade process should be instructions in the Windows screen you.You are trying to do before you upgrade windows 7 beta expired.