I am thinking about getting a pre-order for Windows 7 upgrade, but I don't want to buy it if I can't do clean installs with it. How does the upgrade process work exactly when comming from Windows Xp or Vista? I've poked around on Google, but I have only been able to find documentation regarding the Windows 7 RC to RTM migration.

Would I have to install Windows Xp or Vista first every time I wish to format and reinstall Windows 7 on my computer? Or would I just have to, for example, punch in my old Xp/Vista product key?

4 Answers 4


According to this article, you will need to have an activated copy of XP, Vista, or 7 RC first:

Now here's the bigger catch: While you won't need to downgrade from Windows 7 RC to Vista or XP in order to install Windows 7 final the first, time, you will need to install one of those operating systems and activate it first if you want to do a clean install in the future. Because the Windows 7 upgrade disc will only work with an activated version of Windows. That means you'll need an activated version of Windows XP, Vista, or Windows 7 RC to start with or the disc will be useless.

  • 1
    Original source is here: blogs.chron.com/techblog/archives/2009/07/… Commented Jul 15, 2009 at 14:31
  • Exactly what I was looking for. Although not the answer from Microsoft that I wanted to hear :( Commented Jul 15, 2009 at 14:34
  • You definitely aren't the only one disappointed by this. Commented Jul 15, 2009 at 14:36
  • I wonder if they will leave in a loophole this time like they did with Vista. However, since the term "activated" is being used, I've have to guess there will be no loophole. Commented Jul 15, 2009 at 15:51

You can do it. Paul Thurrott documented atleast 3 different ways to do it:


Method #1: Just perform a clean install

Many, many readers report that they have been able to simply treat the Windows 7 Upgrade media as if it were Full media, and that it just works.

Method #2: Registry hack

  • Change in HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Setup/OOBE/ value of MediaBootInstall from 1 to 0.
  • Run as administrator following command slmgr /rearm
  • Restart
  • Start activate utility

Method #3: The good old "double install" method

  • Install Windows 7 as custom install on clean hard drive
  • Install Windows 7 again now as upgrade
  • Activate it

See that link above for more details.

  • I used Method #2 on my laptop and it worked as advertised. I bought a new larger & faster hard drive specifically to install Windows 7 on and I didn't want to have to reload the OEM supplied (bloat infested) OS only to install W7 over it.
    – Zooks64
    Commented Nov 1, 2009 at 22:15

The upgrade versions will not do a clean install onto a blank hard drive. The install process will have to be started from an already installed and activated copy of windows. You will then be able to choose whether the install does an inplace upgrade (vista only) or installs a clean copy of Windows 7 (in which case the old windows files will be moved to a folder called Windows.Old).


I haven't tested this but it looks like it can be done:

But whether this won't be blocked by MS at some later stage is a whole another deal.

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