Why is my Windows licence not working after reinstall?
Short answer: If you upgraded from Windows 7/8.1 to Windows 10 or 11 using Microsoft's free upgrade, your licence is stored as a digital entitlement — tied to your Microsoft account and hardware fingerprint, not a product key. After a clean reinstall on the same machine, signing into the same Microsoft account during setup automatically reactivates Windows. If activation fails, it is usually because the motherboard was replaced, you are using a different Microsoft account, or the original licence was an OEM licence tied to a machine that was decommissioned.
How to fix — step by step
Step 1 — Use the Activation Troubleshooter first
After reinstalling Windows, go to Settings → System → Activation. If it shows "Windows is not activated", click Troubleshoot. The Windows Activation Troubleshooter checks Microsoft's servers for a digital licence linked to your hardware. If it finds one, it activates automatically. If it asks "I recently changed hardware on this device", select that option and sign into your Microsoft account — this re-links the digital licence to your current hardware fingerprint. The troubleshooter resolves the majority of post-reinstall activation issues without needing to enter any product key.
Step 2 — Retrieve an OEM key from the BIOS
All laptops sold with Windows pre-installed from 2012 onward have the Windows product key stored in the BIOS/UEFI firmware — the low-level software that runs before Windows loads. When Windows installs on the same hardware, it reads this key automatically. If you need to see the stored key (for example, to install Windows on a new drive), run this command in PowerShell as Administrator:
(Get-WmiObject -query 'select * from SoftwareLicensingService').OA3xOriginalProductKeyThis returns the embedded OEM key. Note it down. However, OEM keys are tied to the specific motherboard and cannot be used on a different machine — this is by design. See our Windows key recovery guide for the full OEM key retrieval process.
Step 3 — Check your Microsoft account for stored licences
Visit account.microsoft.com → Services & subscriptions. If you purchased Windows 11 digitally through the Microsoft Store or used a retail box, the licence appears here. You can re-enter it during activation by going to Settings → Activation → Change product key and typing the 25-character key. Retail licences (bought separately, not pre-installed) are transferable — they can be deactivated on the old machine and activated on a new one. Microsoft allows one active device per retail licence at a time. See our Windows activation issues guide for related scenarios.
Step 4 — The India angle: second-hand laptops and OEM licences
In India, a significant share of laptops are bought second-hand — from resellers, offices clearing stock, or individual sellers on OLX and Facebook Marketplace. Many of these machines have OEM Windows licences that the seller has reformatted. A legitimately pre-installed Windows licence on a second-hand laptop is valid as long as the motherboard is the original one. If the machine activates with the BIOS-embedded key, the licence is genuine. If the seller has replaced the motherboard or installed a KMS-activated (pirated) copy, the laptop will show as not activated after every 180 days — requiring a genuine licence purchase. Genuine Windows 11 Home digital licences are available through authorised Indian resellers for around ₹1,500.
When to call a laptop repair service
When DIY ends
Call a technician if: the Activation Troubleshooter returns an error code (look up the specific code — each has a documented fix); the BIOS does not store a product key (common on very old pre-2012 laptops); or the machine was sold to you as activated but shows as not activated — this may require licence verification against the seller.
Typical repair cost in India
Software diagnosis and activation fix: ₹500–₹1,000. Genuine Windows 11 Home digital licence: approximately ₹1,500 through authorised resellers. Windows 11 Pro: approximately ₹2,500.
A note from the LRW Engineer Team
Never use KMS activators or grey-market keys to activate Windows. Beyond the legal risk, these activations break silently after major Windows updates — creating exactly the activation problems customers come to us to fix. A genuine licence is a one-time cost that eliminates this recurring headache.