Change Windows XP location to Drive C

I am using Intel DX58SO Desktop Motherboard in RAID 5 with four SATA 500GB Seagate Barracuda drives. I have installed Windows XP Professional 64-Bit in it. I saw that the default drive for my operating system was set in drive I in RAID. I wanted to change it to drive C but my computer does not allow any changes made in the system disk. Does anybody know how to fix this? Did anyone experience similar problem to this? Please let me know how you fixed it.
