If I remember from when I set up my raid array, you Have to set it up, even if you go on to set it up as "non raid," so to speak.
In other words, you have to tell the raid card "how" to use the two disks. At the moment it does not know what to do with them.
Press F3 when prompted, and one option should be "normal" (IE non raid). Select "normal", and allow the card to do it's thing to the disks.
Then you will have to go into Control panel/administrative tools/computer management/Disk management and "turn on" the new disks. I don't know how to do this bit, as I have never done it.