There may be a partition/HDD initialisation issue.
Run Computer Management (if needed, see https://support.microsoft.com/kb/308423)
In Computer Management select Disk Management.
Examine the listing. Do you see your original HDD plus the new HDD and it's 2 partitions? We're looking to see if your larger partition is in an uninitialized state (not formatted and/or not had drive letter assigned). If it is in this state, you'll need to do this yourself (your partition software might not have completed this).
Be careful, though, make sure you perform this action on the correct partition.