Upgrading Windows 7 release candidate to Windows 7 RTM

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If you are like me, you’ve been using Windows 7 release candidate for months now in your production environment.It was stable, it beat the pants off Windows Vista. The key question for me – how do I upgrade from a release candidate to a release to manufacturer build of the operating system? Microsoft has never officially made such an upgrade possible. However, there is a fairly simple way to step outside the permitted boundaries and upgrade Windows 7 from a beta or RC build to the RTM build of the OS. I got this information from Lockergnome and can report that it has worked like a charm on several different machines.

Here’s what you can do to bypass the check for pre-release upgrade IF YOU REALLY REALLY NEED TO:

  1. Download the ISO as you did previously 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. For example, change 7100 to 7000 (pictured below).
  6. Save the file in place with the same name.
    Run setup like you would normally from this modified copy of the image and the version check will be bypassed.

    These same steps will be required as we transition from the RC milestone to the RTM milestone.

    Again, we know many people (including tens of thousands at Microsoft) are relying on the pre-release builds of Windows 7 for mission critical and daily work, making this step less than convenient. We’re working hard to provide the highest quality release we can and so we’d like to make sure for this final phase of testing we’re supporting the most real world scenarios possible, which incremental build to build upgrades are not. At the same time everyone on the beta has been so great we wanted to make sure we at least offered an opportunity to make your own expert and informed choice about how to handle the upgrade.

    We’re always humbled by the excitement around the releases and by the support and enthusiasm from those that choose to run our pre-releases. We’re incredibly appreciative of the time and effort you put into doing so. In return we hope we are providing you with a great release to work with at each stage of the evolution of the product. Our next stop is the RC…see you there!

    THANK YOU!

    –Windows 7 Team

Bear in mind that this process is not going to be supported if you run into any issues. Microsoft will not help you fix problems that you might encounter. I am not responsible for them either. If you are using a Windows 7 beta or the RC and decide to follow these steps to upgrade your existing environment you should back up any critical data first.