The best I can tell, when using an upgrade edition of a Windows 7 product, it somehow detects an existing installation and saves that somewhere even if you format the drive, then entering an upgrade key will be allowed once system is up and running.

My situation:

  1. A workstation purchased with Windows XP Professional.
  2. Had previously ugpraded (including a format for a clean install) to Windows 7 Professional.
  3. Wanted to move over to Windows 7 Ultimate.
  4. System hard drive in workstation failed, was replaced.
  5. Reinstalled using Windows 7 Ultimate upgrade disk.

Now my install is past the activation time (getting non genuine notifications) and I can't activate since entering an ugprade key results in a dialog informing me that it can only be used for upgrades and I'm not eligible. This makes sense, the current install has no way of knowing that I had a previous version of Windows.

What are the options? What I would like to not have happen is having to reinstall from scratch again, and not only that but first having to install Windows XP just to be able to then install a Windows 7 upgrade.

Any chance that if I called Microsoft and gave them both serials they could give me a clean install serial and I could avoid the hassle?


This site had the answers I needed as well as good explanations of the ins/outs of upgrade installs and when/what is checked.

Edit: the above link appears to be a 404 for now, and I had no luck with the Internet Archive. I think the content may have moved here, or possibly here.

  • It would be a very good idea to have the essential part of the answer in the answer rather than a link, this is precisely why link only answers are bad. – Journeyman Geek Jul 1 '13 at 1:02

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