Activation after hardware change
Windows ties the digital license to your Microsoft account. After a major hardware change (new motherboard), sign into Settings → Update & Security → Activation → Troubleshoot → "I changed hardware on this device recently".
Error 0xC004F074 — KMS not available
This is a volume license / KMS issue common in enterprise environments. Contact IT — the KMS server may be unreachable.
Error 0x803F7001 — No license found
Windows is not activated. If you purchased a retail key: Settings → Activation → Change product key. Enter your 25-character key.
Phone activation
For older keys: slui 4 in Run opens the phone activation dialog. Call the number, provide the installation ID, and receive an unlock code.
OEM licenses
OEM licenses (came with the PC) are tied to the original motherboard. If that board died and was replaced, the license may not be transferable — a new retail license is required.