Now that the RC build is official from Microsoft, users can start downloading the latest RC build 7100 and install it. Microsoft recommends user to do a fresh install even if you have installed the beta version of Windows 7 released in Jan 2009. But it is also possible to upgrade from beta build to RC build using a simple hack. If you want to upgrade from beta to RC, you will need to bypass the check for pre-release as mentioned in the Windows 7 blog.

Windows 7

Steps to upgrade from Beta to RC;

  1. Download the ISO and burn the ISO to a DVD.
  2. Copy the whole image to a storage location you wish to run the upgrade from (a bootable flash drive or a directory on any partition on the machine running the pre-release build).
  3. Browse to the sources directory.
  4. Open the file cversion.ini in a text editor like Notepad.
  5. Modify the MinClient build number to a value lower than the down-level build. You need to change the value to 7000 as it is the beta version build number.
  6. Save the file in place with the same name.
  7. Run setup like you would normally from this modified copy of the image and the version check will be bypassed.

cversion_ini_file

With this change, you can upgrade from the beta version to the RC build.