Activate Windows on the same computer after reinstalling

Question

I had windows activated on this desktop, then I did a clean reinstall and entered the same key. Now it won't activate and gives an error about this key already being used on another device. Error code: 0xC004C008

Answer 1

Hi Trey,

Thank you for reaching out to Microsoft Q&A forum. I understand how frustrating it can be to see Windows 11 not activate after a reinstall, especially when it was previously activated on the same device. To help me guide you correctly, could you please confirm whether Windows 11 came preinstalled on this device when you purchased it, or if you bought a Windows product key separately?

To see what type of Windows license is installed, press Windows + X and select Windows Terminal (Admin). In the window that opens, run the command slmgr /dli. A small dialog will appear showing your license channel, which lets you confirm whether Windows is OEM (preinstalled on the device), Retail (purchased separately) or Volume (managed by an organization).

In the meantime, please try the following supported steps for Windows 11 activation:

Step 1: Run the Windows 11 Activation Troubleshooter

On your device, go to Settings > System > Activation, then select Troubleshoot. If prompted, sign in with the same Microsoft account that was previously used on this PC and choose “I changed hardware on this device recently.” This helps Windows locate and reapply the existing digital license.

Step 2: Use the Microsoft Product Activation Portal

If the troubleshooter doesn’t complete activation, Microsoft now supports activation through the Product Activation Portal.

Using another device with internet access, go to Product Activation portal, complete the CAPTCHA and sign in with a Microsoft account (this account is only used to access the portal and is not tied to your license). Enter the activation details shown on your Windows 11 screen and follow the on‑screen instructions to finish activation.

Please also refer to this official guidance for more details: Activate Windows

If activation still doesn’t go through, please let me know the exact error message or code you’re seeing and I’ll help you with the next supported steps.

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Answer 2

Error 0xC004C008 means the product key has already been used on another device or has been used more times than allowed by the Microsoft Software License Terms, even if it is actually the same physical PC after a reinstall.

To resolve this on Windows 11:

1. Try activating again with the existing key
   • Select Start > Settings > System > Activation.
   • Select Change product key, re‑enter the 25‑character key, and try activation again.
2. If activation still fails with 0xC004C008
   • This indicates the key has hit its activation limit.
   • In this case, a new product key or license is required to activate Windows on this installation.
   • On the Activation page, select Go to Microsoft Store (if available) and follow the steps to purchase a new Windows 11 license.
3. If the device previously had a digital license linked to a Microsoft account
   • Sign in with the same Microsoft account that was used when Windows was last activated on this PC.
   • Then run the Activation troubleshooter from Settings > System > Activation > Troubleshoot to attempt reactivation using the existing digital license.

If these steps do not resolve the issue and the key continues to report 0xC004C008, the key cannot be reused further and a new license is required.

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References:

• Get help with Windows activation errors
• Why can't I activate Windows?
• Troubleshoot Windows activation error codes