Transfer system from IDE drive to SATA raid array

I am trying to transfer my system drive from an IDE disk
to a SATA raid array. I copied everything from IDE to
sata, made it bootable, and succeeded booting from it, but
it keeps being mapped as drive E, and my old IDE as C.
When I remove my old IDE drive, I cant boot anymore : boot
sequence stops with the windows XP logo displayed in the
center of a blue screen
How can I arrange my SATA raid to be mapped as C: ? I
tried the Disk Management tool, and the command line
diskpart, but drive letter assignement for system drive
cannot be modified ...
Please help.

Pierre