I resetted my Windows around 2 weeks back because of a nasty adware, which while most likely partially helped with some extra stuff on the drive, but I also haven't gotten to deleting the windows.old folder which is taking up 11,4GB space on the disk. Program Files and Program Files (x86) only take 5,22GB space combined and AppData has 2,59GB worth of files on it. I have almost 1TB of stuff (mainly games or recordings of said games) on other drives, but then again that's the point of other drives.