One of the many remaining questions about the Windows 7 Upgrade media is how, exactly, a clean install will work with this version of the OS. On the Microsoft Store, the company simply notes the following:
If you have Windows Vista, you can purchase Windows 7 Upgrade versions. You can do a clean install (back up your files, clean install, and reinstall your applications) or an in-place upgrade (Windows 7 installs over Windows Vista).
If you have Windows XP or Windows 2000, you can purchase Windows 7 Upgrade versions. But you must back up your files, clean install, and reinstall your applications.
OK, but what does "clean install" mean exactly? And how does the Windows 7 Setup routine ensure that you have a qualifying previous version of Windows before allowing the clean install? Thanks to an email from Chris P., we have the following info from Microsoft (emphasis mine):
In order to install the upgrade version of Windows 7, you must have a qualifying Windows operating system installed and activated. You cannot install an upgrade version of Windows 7 on a blank hard drive. The installation procedure does not ask you to insert a Windows disc in the drive for verification, the actual qualifying operating system must be installed.
If you do not have a qualifying Windows operating system installed with a genuine license activated, then you cannot use the upgrade version of Windows 7 - you would need a "full version" Windows 7 license.
- A qualifying Windows operating system must be installed.
- The qualifying Windows operating system must have a genuine license (product key) and it must be activated.
- To upgrade, boot to the qualifying Windows desktop, insert the Windows 7 Upgrade disc in the DVD drive.
- When the setup menu appears, select Custom (advanced) to initiate a clean install procedure.
Question answered, right?
The thing is, with Windows Vista, you could actually clean install the OS using Upgrade media, without having a previous Windows version installed on the PC. (I documented this over two years ago in How to Clean Install Windows Vista with Upgrade Media.) Will this method work in Windows 7?
I believe it will. But of course, I will need to test that to be sure. And to do so, I need actual Upgrade media. I've asked. It may be a while.
In the meantime, this is yet another area in which Microsoft could have been far more forthcoming about how the Upgrade process works. There are still far too many unanswered questions here.