14 DAY TRIAL // Windows 10 was released earlier this week and millions of computers have already been upgraded to the new operating system, with Microsoft promising a very smooth experience for everyone performing this upgrade.
As it turns out, however, things are not running smoothly for everyone and plenty of users who are upgrading from Windows 7 or 8.1 and then attempting to perform a clean install are experiencing activation issues, as the process fails with error code 0xC004C003.
Posts on Microsoft's Community forums point to an error message reading the following:
“This product key doesn't work. You might need to get in touch with the store or company you brought Windows from, or you can buy a new key from Microsoft.”
How the activation process works
Microsoft simplified the activation process in Windows 10 to make it easier for users to upgrade from Windows 7 and 8.1, and you can read all details provided by the company in the box after the jump.
But in short, Windows 7 and 8.1 users who upgrade to Windows 10 are provided with a generic key for the new operating system that is then re-used when performing a clean install.
If you install Windows 10 for the first time ever (without upgrading from a previous Windows version), then you need a new key and you cannot use a Windows 7 or 8.1 product key. Right now, the only option to address this is to purchase a new key from Microsoft.
In other words, some of the users who are upgrading from Windows 7 or 8.1 are treated like new Windows 10 users, even if they already purchased a previous version of Windows.
Microsoft says that in most of the cases, this error is caused by server issues, and recommends users to reattempt activation after a few hours. Right now, however, many claim that waiting doesn't make any difference, so if there's indeed some issue, Microsoft had better come up with a workaround very soon because the number of upgraders is increasing at a really fast pace.