Hi,
what does it do on my Windows 10 Pro x64???
- my harddrive before cleaning: 20 GB free
- cleanmgr+ will free additional 31 GB ... wow! :-)
- my harddrive after cleaning: 20 GB free :-(
The hole folder "Windows.old" is not touched by cleanmgr+ ! But 15 MB of thumbnails are deleted, very effective job

I have to go back to the outdatet Windows Tool as long as it works - so I don't understand how to use cleanmgr+ and why not deleting the old WIndows Installation. It's GUI is tricky and irritating for me old school power user. Maybe modern. But very ununsable and laborious.
Hi Axel,
thanks for your comment.
I will invest some more time on GUI Improvement in upcoming versions.
Regarding the Windows.old folder: Did you run the optional script "Windows.old" in "+more" tab. Of course these actions should be run with elevated rights.