Bummer, it only let's you create spanned and striped volumes, not mirror ones. What a silly thing to disable the feature.

You'll have to create the mirror via "hardware" (Bios + Intel utility).

Or you may hack a system file with an hex editor to enable the mirroring (I should have the info needed somewhere). At the next update that system file may (and will eventually) be replaced by a new version uncapable of mirroring, but by then you'll be on the SSD. I don't know whether I'd recommend something like that. I did it once in XP and irt worked, but stil...