OK, after you created the RAID volume, did you save and exit BIOS, re-enter BIOS, and select the single Win7 HDD as the 1st boot drive?Never mind, I just re-read your original post.
Have you installed the Intel Matrix Storage Console (second download on the left-side of the page)
to your Win7 installation?
If not, do it.
Then see if you can set up a RAID volume inside Win7 with the Console.