If you attempt to run the upgrade of Windows 7 RTM on an install of RC1 setup will check a couple of things and then present you with this friendly (not) message: "You can't upgrade this prerelease version of Windows 7. Go online to see how to insall Windows 7 and keep your files and settings."However, just like the beta 1 to RC1 upgrade, there's a simple fix. If you haven't already, copy the install files to a location you can modify, a directory on your drive works great. Then open that directory and locate the CVERSION.INI file in the SOURCES directory. It's a simple text file, so open it with notepad. The file should look something like this: Change the contents of the file, specifically setting the MinClient value to 7000.0, as shown below: Once this is done rerun setup, and Windows will happily upgrade your RC1 install of Windows 7 to the RTM version.
Disclaimer: Upgrading from RC1 to Release To Manufacturing (RTM) of Windows 7 is not a supported upgrade so you do this at your own risk! Having said that, the upgrade from Beta 1 to RC1 wasn't supported either and lots of people, myself included, did that just fine.
Posted by Walden on Thursday, August 13, 2009