How much RAM do you have installed? If Hibernation is enabled, it will take a significant portion of storage based on the RAM.
Try running WinDirStat: http://windirstat.info/
This will give you a nice treemap of your drive.
If you have backup and restore enabled, you likely have many Windows "Restore Points" saved on your SSD. I'm not sure if those are listed in the Properties option you mention, unless "Show Hidden Files" is checked in the file/folder options.
In Disk Cleanup, the More Options tab allows you to delete all the System Restore points except the latest one. If you are Ok with that, you should click the Cleanup button on that tab, complete the Disk Cleanup, and then check your free space, it might help.
Thanks for both of the replies. HIbernation is not enabled (only 4G RAM anyways), and I did delete all old restore points which freed up a Gig or two.
Still very puzzled by this.
aahhhh. In a hidden folder, Pinnacle Studio auxiliary files. 37Gig worth. All set, thanks.
How did you identify the hidden folder?
Thanks for the suggestion. WinDirStat found that my loss of space was in Adobe Camera Raw Cache which was set at 40gb. I do not need that on the SSD.
Purging the cache fixed it - even though the settings for Cache in Lightroom was on E:
I have now gone from 20gb free to 60gb free on my 120gb SSD.
I am most grateful.