Okay, thanks for that.
It shows that there is 527 GB of "unallocated space" on that hard disk (the shaded area). That's where your "missing space" is.
You need to right-click on that shaded area and choose "Create new simple volume".
When the volume has been created, right-click on it again and choose "Format".
When formatting is complete you will have a new drive-letter in Windows Explorer for that new volume. You can store files on it or install applications on it, just like you do on the C: drive.
If Windows won't let you do anything with that shaded area (menu options are greyed out), you will have to boot your computer from a partition management disc which is free from here:http://www.partitionwizard.com/partition-wizard-bootable-cd.html
That boot disc allows you to bypass Windows restrictions because Windows won't be running.