I don't think you can migrate from RAID 0 to RAID 1 direcly... Seems a full backup-restore is required.
If your current RAID 0 volume is less than 500GB, you can simply create a new RAID 1 volume with the new drives and copy everything directly.
Thanks, Edward, that sounds like it might be the correct track.
My next question is, how to back this up? It's a Windows machine, so the backup is problematic becauser the drive in question is the boot drive.
i've used products like Carbon Copy cloner and SuperDuper for the Mac, but there doesn't seem to be any product that can do this with the RAID array. I've tried DriveXML and a couple others, but they fail to copy the data to the new drive, probably because the RAID array isn't accessible when the PC reboots.
Disk clone utility that runs in Windows should be able to copy the data.