XPS 8910, Convert to Non-Raid Disks? Solved!

Upon booting a Dell XPS 8910 I get an message saying there are no RAID disks in the system - though apparently the system is set up for RAID in the BIOS (there is a setting "SATA operation" set to "RAID ON". With the boot message I have an option to press "Cntrl-I" where I can reset the two existing drives to be "Non-Raid" disk.

It seems I have two options to fix the problem - 1) accept the option offered during boot and reset each drive as "Non-Raid" or 2) Change the SATA Operation setting in the BIOS to ACHI instead of RAID. 

Which one of those, if any, should I do? And can I do it safely, as in my disks are not about to be reformatted or something awful like that.

This boot message started appearing after I purchased an SSD, loaded a fresh copy of windows on it, and then re-partitioned the original HDD into one partition (erasing everything else on it, including EFI and recovery partitions).

Thanks for your help.