Windows 7 Beta To RC Upgrade Instructions

I found this great post about upgrading Windows 7 beta to RC. I had this problem, and the fact that it is possible to avoid a full install was very exciting for me.
The original article can be found at www.windows7news.com

The Microsoft Engineering team has outlined how Windows 7 Beta users can upgrade their version of Windows 7 to the soon to be released Release Candidate of Windows 7. The disappointing news is that Microsoft suggests to do a clean install instead as the development changes introduced after the release of the beta of Windows 7 were not always compatible with the upgrades made thereafter.

A clean install on the other hand would mean that all the changes and customizations made to the operating system by the user would be lost. This is a nuisance although everyone knew beforehand that this could happen eventually. Microsoft is suggesting to do a clean install or upgrade from Windows Vista to Windows 7.

The RC, however, is about getting breadth coverage to validate the product in real-world scenarios. As a result, we want to encourage you to revert to a Vista image and upgrade or to do a clean install, rather than upgrade the existing Beta.

The Windows 7 release candidate setup will quit automatically if it recognizes a pre-RC build on the computer system. Microsoft did however publish a workaround for that for users who really need to do it:

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.
7. Run setup like you would normally from this modified copy of the image and the version check will be bypassed.

There you got it. It is still possible to upgrade a pre-release candidate release to the RC of Windows 7. Microsoft did add some words of caution to the article which are quoted below:

These instructions will be brief. Since everyone reading is a well-versed and experienced beta tester you know ALWAYS BACK UP YOUR MACHINE before running any OS installation and NEVER TEST AN OS ON YOUR ONLY COPY OF ANY DATA. Testing a pre-release product means just that—it is testing and it is pre-release. Even though this is a Release Candidate, we are still testing the product. We have very high confidence but even if an error happens once in 1,000,000 we want to make sure everyone is taking the precautions normal for a pre-release product.

One other related caution is INSTALL ONLY OFFICIALLY RELEASED BUILDS FROM MICROSOFT. It will always be tempting to get the build with the “mod” already done but you really never know what else has been done to the build. There’s a thrill in getting the latest, we know, but that also comes with risks that can’t even be quantified. For the RC we will work to release a hash or some other way to validate the build, but the best way is to always download directly from Microsoft.

It basically says to avoid unofficial releases of Windows 7 and to make sure that data has been backed up before starting the installation of beta and release candidate builds.