After installing an OEM replacement HDD in my x540, I bought a flash drive on Amazon for$10 that rebooted my Windows 10 and it's working like a brand new machine.

I believe the product key for windows 10 is embedded in motherboard.

And thank you Padraic

After installing an OEM replacement HDD in my x540, I bought a flash drive on Amazon for$10 that rebooted my Windows 10 and it's working like a brand new machine.

I believe the product key for windows 10 is embedded in motherboard.

When removing both cables there is a small black plastic flap covering the connection.

GENTLY lift that flap and GENTLY lift the end of the cable/ribbon and you're good to go.

My first try I was under the impression it was more of a plug and didn't see any specifics just like above “remove cable” but no description of how.

Even though I did it wrong, it didn't damage anything, and this guide was a big help.