After performing a clean install of Windows 10, reinstalling my software and restoring my data, I noticed that my Windows partition was considerably larger than it had been prior to upgrading from Windows 7. At the time, I simply assumed that Windows 10 was larger than Windows 7. I accepted that as a reasonable explanation, but couldn't help but notice other symptoms that my partition was growing. I use Acronis's True Image to create a backup of my partition every day. Those backups took longer and longer as the partition grew.
A couple of months after installing Windows 10, I attempted to create a number of virtual machines using both vSphere and VMware. I was not successful. What is significant about that is that I had trouble removing the virtual disks from my system. Recently, while trying to figure out what was taking up all the space on my disk, I came across a 70 gigabyte file under the Virtual Machines directory tree. When I tried removing it, I was denied access. With the help of experts on this site I managed to overcome that obstacle and get the directory removed. Much to my amazement, that single action reclaimed 500 gigabytes of space!? I don't know where the other 400+ gigabytes came from, but I suspect there was something hidden within the Virtual Machines directory tree. The amount of the C: partition being used went from approximately 800 gigabytes down to 282! The next time I ran a backup, it finished in half the time!
Approximately one week later, the C partition contains almost 650 gigabytes! Last night the backup took almost 7 hours! I don't know what's filling up the C partition. During the last week, I did try installing Windows 8.1 in a virtual machine. Once again that failed and I removed the Virtual Machines directory. Otherwise, I have made no other attempts to install new software. I couldn't help but notice all of the recent Windows update activity. I don't know whether that's the culprit. The only other thing that occurs to me is that something on my system is populating logs, but I'm not sure what that could be. I used to get a message stating that "Scan to disk has stopped." I have no idea what that is.
I use Dragon speech recognition. I've often suspected it of being responsible for anomalous behavior. Specifically, I believe that it frequently updates some sort of profile data – the result of which is degraded system performance. When it stopped working the other day, I removed and reinstalled it. I wonder whether it's what's gobbling up my partition. I guess there's one way to find out.
Anyway, if anyone can tell me what Windows 10 facilities are available for tracking disk usage, I would appreciate it!