Fix This computer's hardware may not support booting to this disk, Ensure disk controller is enabled in BIOS, Windows cannot be installed to this disk.

Fix Windows cannot be installed to this disk. This computer's hardware may not support booting into this disk. Ensure that the disk's controller is enabled in BIOS.

So I was flashing the firmware on a spare HP DL380 G6 to the latest (firmware DVD 930) Going through the BIOS menu afterward I noticed that the default for Advanced Options > Drive Write Cache is ...