Hi there,
Unallocated space means the HDD has been partitioned, but no file format has been added to the drive.
Tell the group about your HDD, brand, size model #, and what you have done to the drive. ie, is it new, has it been working on a commercial desktop or laptop, does it have 1 or more partitions on it, is it used as a system disc, do you have important data on it, etc. That way we will know how best to advise you.