I have been racking my brains trying to find out where in the heck I was losing 468 GB of storage on my 500 GB drive. I was able to determine where (System Files) but other than that without having to drill into many paths and files.  I followed the directions here and downloaded TreeFree and was able to quickly find a monster windows.edb file. I then had to stop the windows search service to free access to the file. Doing so via Services would not work so had to go Command Line options to