New RAID setup

I want to create a RAID 1 mirror set for my Vista drive. It is installed on
a 300GB hard drive. My old XP load is on my other 300GB drive. I'm ready to
wipe out XP and create the mirror set. The documentation on the Intel
Matrix Storage Manager isn't clear. When I tell it which disks to include
in the mirror set, can I specify which drive should be original and which
should be the copy to get this going? It looks like it will wipe out both
drives and expect me to load from scratch.