According to Microsoft, it is not possible to directly or in-place upgrade from Windows 7 Beta or pre-RC build versions such as build 7077 (32-bit Windows 7 Build 7077 or 64-bit Windows 7 Build 7077) to final RC (Release Candidate) build, which widely rumored to be build 7100. The blocking of direct upgrade from beta or pre-RC builds to official RC build is meant to avoid potential issues that may affect such upgrade path.

Microsoft recommends Windows 7 beta testers to restore and reinstall Windows Vista prior to upgrade to Windows 7 RC, or perform a clean installation of Windows 7 RC. 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. Build-to-build upgrade within Windows 7 builds may fail, or encounter error, such as setup does not success completely or unable to set some settings. Beside, Windows Vista to Windows 7 upgrade is what will most likely occur in reality when Windows 7 is finally released to shelf, as end-users probably won’t install any non-final or non-RTM product.

A mechanism has been built into Windows 7 RC to identify non-Vista Windows OS, and block or prevent upgrade of OS from Windows 7 Beta (build 7000 till 7099) and all pre-RC development milestones to final Release Candidate milestone. Users are encouraged to install Windows 7 RC with clean installation (fresh install) method, or use the Windows Easy Transfer feature to save and transfer accounts, settings, files, personalizations, and others from current installation to newly installed Windows 7 RC system. However, there is also a hack technique to circumvent and bypass the limitation.

When trying to upgrade Windows 7 pre-RC build to Windows 7 RC, but been stopped and cannot continue with installation process, before been force to exit gracefully, use the following trick to to upgrade successfully from pre-RC (build 70xx series) to RC (possibly 71xx series).

  1. Download the Windows 7 ISO.
  2. 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.

  3. Browse to the sources directory.
  4. Open the file cversion.ini in a text editor such as Notepad.
  5. Modify the MinClient build number to a value lower than the down-level build. For example, change 7100 to 7000.

    cversion.ini

  6. Save the file in original place and original name.
  7. 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.

It’s expected that the next development milestone of Windows 7 – Windows 7 RTM will also be blocked from upgrading directly from Windows 7 RC. If so, the hack above can be used to skip the version check too.

Update: How to in-place direct upgrade from pre-release version of Windows 7 to Windows 7 final RTM build.

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