What's the output of fdisk -l?
You might have been better off just making one partition for vista, and leaving the remainder of the drive as free space for Fedora to detect, partition, and format.
Apparently Fedora doesn't recognize the partition type for vista (or the partition table used by vista) and just sees the whole disk as one partition.
Try a liveCD. Does it see two vista partitions, or just one? That could tell you whether it's a Fedora problem in particular, or a Linux problem in general (in re vista partition type and partition table).