Have you tried goog...
That's strange... Defragging needs extra space for allocating and moving files around. It's almost as if it allocated the space, but didn't clear it when it was done defragging. I don't know how much space defrag allocates, but I wouldn't think it would be twice the original 'file' size.
Have you tried running it again? Maybe with a different defrag program.
Try HDGraph to see what is taking up the space:
http://www.hdgraph.com/