Running Low On Drive C Space

Within the last month I began seeing this message. I ran Disk Cleanup, and even uninstalled some little used programs, but I kept running low. For years I've kept a compact system volume of about 28GB in the logical 30GB C partition. All User info is on other drives. I've never run short of space before, but just to give me some room, I used Mini Partition Tool to add an additional 5GB to the C partition. This "filled up" within a week without me adding any programs, and now I'm getting the message again. I've tried Disk Cleanup, CCleaner, etc, with no improvement. This is my current status:







I'm at a loss with this because WinDirStat shows what has always been the historic size of my Boot Disk, but the others do not. Can someone help me solve this dilemma? Thanks

I noticed that TreeSize showed a 10GB folder called System Volume Information, which was not identified by WinDirStat. On Googling it, I found that it contained restore points. A thread in Tom's Hardware showed how to reduce its size in Advanced System settings. I reduced it to 2GB and now have plenty of C drive space. I manually back up the Boot drive weekly using Macrium Reflect, so I shouldn't need many restore points. TreeSize proved to be more useful than WinDirStat in this case. I'll leave this thread open for a few days to allow other responses, and to see what happens.

One does want to keep System Restore working even with a smaller size than the default as a number of install and uninstall routines and cleanup programs tend to create a new Restore Point before doing their work. Then of course there may be another created at the next bootup.