It took me a while to google this gem of info since I really didn't feel like reinstalling Windows 7 just to enable raid!
I have two pieces of information to share with those of you looking to enable RAID on your Windows PC after having installed Windows without RAID enabled. Now that you have rebooted past a handful of blue screens and Googled to find some help, I am here to tell you that you have come to the right place.
Use at your own risk since officially the Intel website says this is not possible and you need to reinstall windows LOL!
Working fine so far with Windows 7 RTM with latest Intel raid drivers on DP35DP motherboard.
It's scary seeing all the problems with operating systems prior to Windows 7 though.