Windows 8, Windows 8.1 and Windows 10 TH1 and TH2 had edition specific installation issues. Your key may be a Single Language Edition or a with Bing Edition and hence rejected by installation media of the wrong Edition. From Windows 10 TH2 and later all Windows 8.x and 7 OEM keys are treated as Windows 10 keys. Edition specific installation problems were fixed with Windows 10 RS1. The Windows 10 RS1 .iso is multi-edition. It contains all OEM Editions and will automatically pickup a Windows 8/8.1/10 UEFI BIOS OEM System Locked Preinstallation key and automatically install the correct Edition of Windows 10: [URL] 
My hard drive died in my Inspiron 660. I ordered a new hard drive and a Dell USB recovery key. Dell recommended a recovery key for Windows 8 pro based on my service tag. I installed the new drive and used the recovery key to install Windows 8 pro. I then used a third party tool to get the product key from the BIOS. The product key does not work. I'm wondering if the product key on the BIOS is for Windows 8, not Windows 8 pro. If so, Dell recommended the wrong recovery key. What do I need to do to successfully activate Windows? Secondly, on my old hard drive, I had upgraded to Windows 10 when it was a free upgrade. How do I get the free upgrade back?
had to install new hard drive, windows key not working