I just tried running the utility. In my case it is CTRL+F. It is only possible to launch it if AHCI Controller is set to RAID in BIOS. Strangely, my two 2 TB HDDs do not show up in the utility. Only my 1 TB HDD is listed. But all 3 HDDs are connected on the relevant SATA ports. I did disable the 2 TB HDDs in Windows, but that should not affect their functionality before Windows?!
EDIT: I confirmed that Windows's settings do not influence what shows up in BIOS or the RAID utility. Strangely, I noticed that in BIOS only my two 2 TB HDDs show up, whereagainst in the RAID utility only my 1 TB HDD shows up. That is just the opposite of what I need. The RAID guide does not mention anything about (in-)compatibility.
My mobo is the ASRock 980DE3. My two 2 TB HDDs are connected to the SATA2 ports. The SATA3 port is populated with an SSD. My two 2 TB HDDs are Western Digital Green.