According to Microsoft, it is not possible to directly or in-place upgrade from Windows 7 Beta or RC build versions. A few tweaks and enhancements have been introduced during the development process, which can enhance support of Windows Vista to Windows 7 build-to-build upgrade.
Download the Windows 7 ISO.
- Burn the Windows 7 ISO image to a DVD, and then copy and whole image to a storage location that you wish to run the upgrade from (can be either any directory/folder on any partition/drive on the machine running the pre-release build, or a bootable USB/FireWire flash drive).Alternatively, it’s possible to directly extract the content of the ISO to a desired folder using file extraction tool such as WinRAR.
- Browse to the sources directory.
- Open the file cversion.ini in a text editor such as Notepad.
- Modify the MinClient build number to a value lower than the down-level build. For example, change 7xxx to 7100.
- Save the file in original place and original name.
- Start the setup process of Windows 7 as per normal from the modified copy of the installation files, and the version check will be bypassed.