Although Microsoft officials claim that Windows RTM does not support direct upgrades from the RC version, when users run the RTM installer directly on the RC version, they will find that the upgrade installation option is not available and can only use a custom installation method. The original system files will be moved to a Windows.old folder. But in fact, this is only a "scare" argument, because the way to crack the limit has already existed, and Microsoft's existence of this method has been ignored, seems to acquiesce to such changes.
Someone might have thought of it, yes. Modify the Cversion.ini file in the installation image just as you did from beta upgrades to RC. A number of people have successfully upgraded to Windows 7 RTM using this method, as follows:
The download back of the ISO image file unpack;
Enter the "Sources" directory;
Open the "Cversion.ini" file with any text editor;
Change the second row "minclient=7233.0" in 7233.0 to the RC version number 7100.0, save and close the editor;
But here's a reminder, although this method can be installed on the RC version of the installation of Windows 7 RTM directly, but there may be some uncertainty caused by the future use of some unexpected situation, so do not encourage people to upgrade the installation directly, presumably this is the original intention of Microsoft to limit it.