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.

1. Download and burn ISO to a DVD.
2. 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).
3. Browse sources directory.
4. Open cversion.ini in a text editor.
5. 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.
6. Run setup like you would normally from this modified copy of the image and the version check will be bypassed.

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