I first purchased Windows 7 Home Edition (32-bit), then upgraded online to Windows 7 Pro (32-bit). The hal.dll corrupted and I couldn't fix the problem because I only had the Home Edition discs.

Several sources in Forums advised me to fix the problem using a boot disk from an ISO downloaded from Digital River. That disc couldn't fix the hal.dll problem either so I did the Custom Install.

That put a new installation of Windows 7 Pro on the computer. Now I'm being asked for the Activation Key. The Key I was given when I upgraded to Pro isn't being accepted. I'm told that the Key I was given only works for the Windows 7 Pro upgrade..!

I've signed-on to the Microsoft site and followed links around for a while, but I can't find any understandable information about my problem.

How do I get the Activation Key for Windows 7 Pro now that it's been reinstalled?

  • Windows only requires an existing directory called "Windows" to exist. You can just make one with the "cd" command. Documentation is here. – David Schwartz Aug 14 '13 at 4:17

Officially you can't use an Upgrade key to do a clean install. However Paul Thurrott posted a guide how to do this:

  • Open regedit.exe with Start Menu Search and navigate to:

  • Change MediaBootInstall from "1" to "0". (Double-click it and then enter 0 in the dialog that appears.)

MediaBootInstall regedit.exe

  • Close RegEdit.
  • Open the cmd by making a right-click on cmd in Startmenu search and select "Run as administrator."
  • Run this command inside the cmd Window:

    slmgr /rearm
  • Reboot

  • Activate Windows 7


Another way of doing this without messing around in the registry is to simply use your Pro ISO inside windows and do an in place upgrade. You can do an in place upgrade from the 30 day trial of Windows 7 (when you don't enter a key) and even upgrade to exactly the same version as you are already on. Your key will then be valid. The only downfall is you have to install windows again!


Thanks everyone for the advice.
I turned for help from Microsoft service-by-telephone and while the Tech. was working on my computer remotely I watched him try a few methods including what's been described here. I'm not sure why it didn't work for him either but the Tech. in turn asked someone in another department for help.
Once my OS was authenticated a new Product Key was generated and now the OS is Activated.
I've learned to ensure I have a Product Key that the Activation process recognises and accepts and that the current version has been Activated before I install any Updates or applications.

(I also learned that if I telephone Microsoft mid-day I'd better have packed a lunch and brought a book with me...)


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