Windows 7: Unaccountable Disk Usage - WinDirStat vs Drive Properties

Hi SevenForums, this seems like a great forum and I hope one of you can figure out my problem. I have x2 1.5TB WD CaviarBlack HHD. I have my primary drive partitioned to about 900GB for C:\ with 500GB unallocated. The second drive is for backup and is formatted as Dynamic with all space except a static 500GB partition going to auto-backup. I believe when I setup Windows I gave 500GB to the backup partition as well, but it has since grown automatically to allow for backups. It is now full and it shouldn't be.

Anyway, the reason it's full is because of some oddly unaccounted for space on my primary C:\. When I look at WinDirStat, the C:\ is supposedly only using 245GB. However, when looking at drive properties or in Disk Management, it shows that 595GB are being used! I can't figure out where the extra 250GB is going. So weird and I know it's not a backup since the backups automatically go to the other hard drive.

Here is a picture of WinDirStat (C:\ only) along with C:\ properties.

Hello Steelsouls and welcome to Seven Forums.

I'd start with this tutorial and see if any hard drive space can be recovered.

Hard Disk Space - Free Up and Recover