how to personalize or activate my windows even though i do not have product key because i bought my pc from normal shopping center

To activate and personalize Windows without a product key, the options depend on how the PC was originally sold and what license it has.

1. Check if the device already has a digital license or embedded key

• Many PCs sold in stores come with Windows preinstalled and a product key embedded in the firmware or stored as a digital license.
• Connect the PC to the internet.
• Open Settings → System (or Update & Security on Windows 10) → Activation and check the activation status.
  • If it shows as activated with a digital license, Windows is already genuine and activated; personalization (wallpaper, themes, etc.) will work.

2. If Windows shows “not activated” or asks for a key Windows requires either a digital license or a 25-character product key to activate.

Typical reasons it is not activated:

• The seller reused the same product key on more PCs than allowed.
• The PC has a counterfeit or non-genuine copy of Windows.
• A different version/edition of Windows was installed than the one originally licensed.

In these cases:

• If the PC was sold as new or refurbished with Windows, ask the seller for:
  • The original Windows DVD/USB and
  • The product key or Certificate of Authenticity (COA) that came with the device.
• If the seller cannot provide a valid key or media, or activation still fails, a new license is required.

3. Buy a Windows digital license from Microsoft Store If there is no valid key or digital license:

• On Windows 10:
  1. Go to Settings → Update & Security → Activation.
  2. Select Go to Store.
  3. Purchase a Windows 10 digital license.
• On Windows 11:
  1. Go to Settings → System → Activation.
  2. Select Go to Store.
  3. Purchase a Windows 11 digital license.

After purchase, the license is linked to the device and Microsoft account, and Windows should activate automatically when online.

4. If Windows was never activated on this device

• For a device that has never had an activated Windows copy, a valid product key or a purchased digital license is required to activate.
• Without activation, some personalization features remain locked.

5. If hardware was changed (for example, motherboard replaced)

• If Windows was previously activated and hardware was changed, use the same Microsoft account and follow the activation troubleshooting and reactivation steps described in the activation and hardware-change guidance.

If none of these options work and there is no valid key or digital license, the only supported way to fully activate and personalize Windows is to purchase a genuine license.

References:

• Why can't I activate Windows?
• Activate Windows
• Reactivating Windows after a hardware change