Unallocated generally means your partition table got hosed. Do not create a new partiton unless you have to as this will overwrite all existing file and folders info.
Years ago, I learned by accident that if I store or try to store more than 128 files in the root, the drive becomes unstable, loss of data occurs and one day only one file or folder was there. I still believe that is true. Unlimited files on the drive, but only 128 max in the root.
There are 2 utilities, specifically FFR and FFU (FastFile Undelete and Recover) that will access your locked or inassessible HDD and let you get those files back, BUT you have to prepare a place for them first - not on the same drive.
I have used FFU and FFR many times when all else was 'lost' so I recommend you invest $29.95 or whatever it costs now and get a copy.
I too had a 200Gb HDD that I was merrily 'stuffing' with certification and techie goodies, when one day it was all gone. FFR got 90% of it back. There were over 200 files ion the root too,
has the free demos. Grab them and see whats still retrieveable/readable.