Upgrading your Windows 7 RC to RTM
Initially Windows 7 RTM will not let you upgrade your Windows 7 RC installation directly. However I found a simple work around from http://www.howtogeek.com . link here: http://www.howtogeek.com/howto/3075/how-to-upgrade-the-windows-7-rc-to-rtm/
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Read the complete post at http://msforums.ph/blogs/jayr/archive/2009/08/14/upgrading-your-windows-7-rc-to-rtm.aspx