I have an XPS 8500, purchased in 2012, originally with Window 7 pre-installed. Last year I purchased a retail Win 8.1 Full Version and upgraded the pc. But, now I can't seem to update that to Windows 10.
I downloaded and ran the Windows 10 media creation tool and tried an update now: result, 0x8008005 0x90016 error.
Also ran sfc /scannow, rebooted, and tried again, but same results.
I then created a USB 64-bit offline install, booted from that, but it would not accept my original Dell Windows 7 key, nor would it accept my retail WIndows 8.1 Home key.