One way would be to back up your installation using Win 7 Back Up on to however many DVD''s it takes or maybe an external HDD. Configure your SSD's to RAID 0 and then recover the installation off your backup. I haven't done this myself but I think it should work in theory.
So I take it that there's no way to easily do this without moving my files off the drive?
Unless you have two new drives to raid with. If planning on using your existing drive, you will have to back-up all files and reformat to match 2nd drive.
Have you considered using your ssd as your OS drive and adding 2 satas for raid?