You are trying to free up a few GBs on drive C? You tried to clean WinSxS folder, you have tried Disk cleanup util and even the Dism.exe but still need a few GBs of free space? ;)
You got to the right place - your problem is Dropbox.
- Go to the Program Files (x86) > Dropbox folder
- Delete all Client XX.XX folders except the latest one
You will be amaized that it will free up to 2-4 GB of space! :)
Thank you and see you ;)