My pc was shipped with windows 8 installed, then took the free windows 10 upgrade when offered.
Since then, my system has crashed, ant I cant reinstall 8 from the included recovery disk without a product key that was never included(they say it is embedded in the motherboard).Nor can I get a windows 10 image for my pc, because it wasn't installed when I bought the computer.
Windows 10 will install and work without needing a key etc.
You need to buy an OEM System builder DVD and when or if it prompts for a key tell it you do not have one.
Then install 10 clean and go online and it will activate automatically.
The disk works with All Dells from 2006 and later.
Drivers for things like Audio, Video, Chipset, etc may need to be downloaded as the OEM drivers are not part of windows.