One thing I forgot to mention that I think is probably doing this is I have Diskeeper 2010 Pro with HyperFast installed. And the HyperFast feature is an SSD auto optimizer.... so I'm willing to bet that's what I was seeing going on and just happened to notice it this one time. That makes sense. I haven't been able in the past to find out exactly how the Hyperfast works but I'm willing to bet it acts just like the other SSD optimizers where it fills the drive then clears it.
When I run WinDirStat on my C: SSD I get 18.6GB taking up "Unknown" space. Anyone have an idea how I can figure out what this unknown space is?
When I uncheck show unknown space in WinDirStat it show me the same amount of space used as when I highlight all files/folders and do properties, 39.1 GB used.
But haven't been able to figure out this mystrious 18.6GB taking up space.
I found what the "unknown" data is now. It's my "System Volume Information" folder for restore points. I didn't have permission to view it then and now I do and that's where my missing used up space is.