Did you used software like acronis (or how was it clled) or other partition managers?
if so, then the answer is not the one you're gonna like because I got the same problem when partitioned my HDD and couln't access the partition I needed. The only thing that helped me that time was booting up win XP install and deleting the partition and making a new one instead (hell of a lot files I lost there, about 500 GB).
If the info there is worth it, then I suggest you go lazer blazing looking for programs related to partitions and try doing something about it, and may the google be with you.
If the info is something you can recover manually (download for example), then it's not worth spending hell of a lot of time restoring it, and may the formating god be with your hard drive.