Windows 7 upgrade attempt fails with message “The upgrade was not successful” and results in an upgrade reboot loop.
When attempting to upgrade from Windows Vista or Windows 7 to Windows 7 the upgrade attempt may fail and display this message:
The upgrade was not successful.
Your previous version of windows is being restored.
Do not restart your computer during this time.
However, when the system restarts it does not roll back to the previous version of Windows, continues with the upgrade and fails with the same message again. This occurs repeatedly and the process is stuck in a loop.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB978421.