Non-RAID in RAID mode

I recently got 2 extra HDDs to add to my rig (now making 4) I previously had the other 2 in RAID 0. When I got the new HDDs I was planning on using the 2 new ones in RAID 0 as my OS drive and the other 2 not in RAID just as data drives. While re-installing windows both of the older, non RAID HDDs showed up but when I go into Computer all I get is my RAID HDDs and my external HDDs.

I just wanted to know if it is even possible to have your non RAID HDDs show up when your BIOS is set up in RAID mode.

If it is possible would someone be so kind as to tell me how to do this?

Thank you very much!