XPS630 raid 1 mirror- my computer showing C: and E:

​My system was delivered with (2) 500gig HDD in Raid1 mirror. It appears that the Mirror is no longer active and I am getting corruption notification notices in the boot cycle. I now am showing an extra drive (E:) where there was none before and it is reporting a similar size as my (C:) drive . What should the Bios settings settings be for Raid 1 mirror? How do I fix the problem with C: having less free space than E:?​

​thanks​

​Sean​