Migrating from SATA to RAID

I decided I'd like to begin using a RAID-1 array for redundancy. Currently, I have a 1 TB Western Digital hard drive that I use as my primary disk. I backed it up with ATIH 2011 and saved the backup to an external 1 TB hard drive.

Next, I bought an identical internal Western Digital hard drive. I installed that in my machine, configured the RAID set and created a 931.5 GB NTFS primary, active partition. (931.5 is the maximum size due to how drive sizes are calculated).

I booted up my ATIH 2011 rescue media, found the backup on the external hard drive and chose to restore My Disks. After choosing to restore the entire drive, including MBR and Track 0, I get to the destination selection prompt. I see my RAID hard drive in there, 931.5 GB (the same size as the initial disk that I backed up--one of the drives in the set actually IS the drive I backed up!) and I attempt to choose that disk. However, it is grayed out!

Is there something wrong with restoring a SATA backup to a RAID set? Is there a better way to migrate from a single SATA Windows 7 drive to a RAID-1 array preserving all of my DATA in the process?

Please advise.

Happy New Year!