HOWTO: Upgrade Windows 7 beta to RC1 directly

Follow these steps to perform a hack upgrade of your Windows 7 beta to RC1

1. Obtain the Windows 7 RC1 ISO file.
2. Extract the content of the ISO file to a folder using utility like IZArc
3. Inside that folder, open the sources directory.
4. Open cversion.ini in Notepad or similar text editor.
5. Change the 4-digit number after the word MinClient build number to a lower value, like from 7100 to 7000.
6. Save the file.
7. Start the Windows 7 installation
8. When presented with the option of Upgrade or Clean Install, choose Upgrade….voilà!