Reloading windows 8 or 8.1 with a failed Hard Drive

Hello all We are a computer repair shop, we seem to be having the same issue other shops and or people are having, Reloading windows 8 or 8.1 on a system that the product key is embedded in the Bios. We have research this problem and a lot of the time, the answer is completely wrong or off topic. Scenario only concerning windows 8 or 8.1 any version, also data recover is not a concern:...