5820 Tower Win 10 installed on wrong drive.

Have you asked Dell tech support about this mix up, one would think that your warranty would cover this type of situation.

This Dell webpage has three methods of installing an OS to a NVMe SSD as the Boot device.  I have used Method 3 with some success after removing any other hard drives before the attempt.

Got fed up of being bounced around by Dell tech support, hence the decision to rectify the problem ourselves. I have a fully functioning system with Win 10 on the SSD, but in legacy mode ( which according to Dell’s own article shouldn’t be possible) and secure boot disabled. I tried method 3,but couldn’t get a driver to load when I got to the where do want to install Windows section, and the SSD wasn’t listed. Is there a specific location required on the USB key being used?

Make sure the SSD is partitioned as GPT not MBR.

That was part of the original problem, when the SSD was formatted as GPT it wasn’t recognised by the UEFI and wasn’t an option for the installation destination. Changing to MBR and running in legacy cured this, but then you can’t enable secure boot. Finally after some trial and error I’ve finally managed to achieve the desired result.

I reformatted the drive to GPT set the bios to UEFI with secure boot enabled, and disabled all the SATA drives, and started the installation from USB, this got me to the where would you like to install Windows screen, but no drives where visible. Attempts to load a driver were initially unsuccessful using the Samsung driver package, I then downloaded and extracted to another USB the Intel Rapid Storage Technology driver. I was then able to load this from the install screen,and away it went, clean install on the SSD in UEFI mode with Secure boot, “happy days”. Finished the install went back to the bios re-enabled the SATA drives, downloaded and installed any missing  drivers from Dell, and all’s fine.