If you do follow the steps below, you might run across some oddities after upgrade. So when you try to upgrade a Windows 7 pre-RC build you will find that you’re not able to and setup will tell you and you can then exit gracefully. You can install as a clean installation and use the Windows Easy Transfer, if you wish to move your accounts, settings, files, and more. To bypass the version check, the instructions below will use a mechanism that is available for enterprise customers.
- Download and burn ISO to a DVD.
- Copy the whole image to a 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).
- Browse sources directory.
- Open cversion.ini in a text editor.
- Modify the MinClient build number to a value lower than the down-level build. For example, change 7100 to 7000. 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.