In previous Windows releases, when you installed an upgrade version of Windows: if you wanted to reinstall the upgrade version, you had first to reinstall the qualifying version from which you upgraded, reactivate it, then upgrade again and reactivate again. There is no need to know your Windows 10 product key see ‘Understanding Product Activation in Windows 10:.Activation servers might be overwhelmed at times because of the volume of upgrades, so give it some time if you get an error message such as (0XC004E003, 0x8007000D, 0x8007232b, or 0x8007007B.) Windows 10 will eventually activate as long as you upgrade using the appropriate method.If you are prompted to enter a product key, click Do this later and give it a few days, Windows 10 will activate automatically.If you perform a clean install on the first attempt, you will have to start over from an activated Windows 7 or Windows 8.x installation.By default, Windows 10 builds are pre-keyed, meaning, you do not have to enter a product key and should not be prompted to enter one, as long as you upgraded from an activated Windows 7 or Windows 8 or Windows 8.1 license or Windows 10 Preview build.Windows 10 uses its own unique product key. A Windows 7 or Windows 8/8.1 product key cannot activate Windows 10.Understand and Fix Windows 10 Product Key Activation How to Find Your Product Key After Upgrading to Windows 10.How to Find Your Windows 10 Product Key.For more on activation issues, take a look at these articles: Update: This was written for issues when Windows 10 was initially released in 2015. Regardless of this, product activation remains a part of Windows 10. In this article, we take a look at product activation and troubleshooting steps.

The most notable being that Windows 10 is free for existing Windows 7, 8/8.1 users for the first year.

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