Dell OS Media Asking for Product Key

Use the Windows 10 Build 14393 RS1 .iso from Microsoft:

http://dellwindowsreinstallationguide.com/download-windows-10-oem-and-retail-iso/ 

https://www.youtube.com/playlist?list=PL1RkaknDn7v-Ucth4gt0U3BHVSY7oNkWr 

The Windows 10 Build 14393 multi-Edition .iso been designed to accept the Microsoft Digital Marker (MSDM ACPI table with 25 digit OEM SLP key) from all Windows 8.0 OEM, Windows 8.1 OEM and Windows 10 OEM licenses alleviating all the issues similar to the one you are experiencing.

Thanks for your reply. I tried what you suggested but this is also asking me for a product key.

Continue the installation of Windows 10 by skipping input of the Product Key. After Windows 10 is installed, install a program called RWEverything. Let me know if the system has a MSDM or SLIC table present. Also let me know what Microsoft Genuine Label is affixed to the system. Details on doing this are here:

https://www.youtube.com/watch?v=TRhS8hsMjls 

http://dellwindowsreinstallationguide.com/uefi/ 

Hi Philip,

Thanks for your response. There is a SLIC table but I cannot see a MSDM table. Also, there is a sticker on the bottom of the laptop that just says "Windows 8".

Kind Regards,

Tiffany

If there is no MSDM table then your UEFI BIOS has lost your Windows License. This happens extremely rarely I have only seen it happen about 5 times and I have helped out quite a bit with OS Reinstallation.

In one of these rare occasions the customer fixed it by flashing their UEFI BIOS to the latest version. If its an XPS 12 L221x the Latest UEFI BIOS Update is x39:

http://downloads.dell.com/FOLDER01768849M/1/MUR_A08W.exe

If flashing to the latest version doesn't give you the MSDM table back we can probably unofficially install Windows 7 Home Premium using OEM SLP which will use the SLIC. Then connect online to get a genuine ticket. One can then use this genuine ticket with a clean install of Windows 10 Home to perform the initial activation and then your system will be a Windows 10 Home Device in the same manner if the SDM was still present.

Flashing to the latest version didn't bring back the MSDM table :(

How do I install Windows 7 using OEM SLP?

I've put some details together here on Downloading Windows 7 Installation Media and applying OEM SLP:

http://dellwindowsreinstallationguide.com/windows-oem-faqs-and-downloads/