As hang-the-9 stated, there must be something wrong. Win will not assign the same drive letter to two partitions at the same time. Can you post a screen shot from disk management? What happens if you try to change the drive letter of the second partition?
I think when I tried to clone the original 500GB system volume to the new 1TB drive, the EaseUS software created this mess. I have attached a screen shot of drive C, Disk 1.
I want to get rid of the partition and mirror with Drive 2. The RAID-5 is for my data.
I am stumped.