Defraggler eats all of my free space

I was defragging my external HDD and it stopped halfway due to a power outage. Now, my free space went from 500 GB to about 150 GB. I added up all of the folders that are on the drive (with TreeSizeFree) and they only add up to about 500 GB. How do I reclaim my free space that was lost from Defraggler?

Note: I've deleted all of my Restore points and no success. Ran CCleaner repeatedly