I was prowling BIOS settings to resolve a different problem. I noticed that the BIOS is set to run SATA drives in RAID, rather than AHCI. Which should I use?  I have a single HDD in the system now. Probably will go to a SSD (Boot) and HDD (Data) in the future (next week). 

Windows 10
BIOS 2.0.1 (not upgrading!)
No plans to use Raid 

I saw this thread: https://www.dell.com/community/Desktops-General/AHCI-disabled-on-XPS-8900-desktop/td-p/4673037/page/2  which leads me to believe RAID is the "factory default", and that I will have some small, manageable hoops to run through to make the switch. 

Thoughts?