What happen is that I install the dropbox and activate the sync. All files has been saved on my hard drive, filling up all space. I then unistall dropbox, but the files were still there. I then read I shall de-activate the sync to remove the files, so I attemp to install dropbox again but the installation always fail. What can I do? Thank you for your help.
At first, note that what you initially describe is expected behavior since this is exactly how our desktop app works. When you install it for the first time, a Dropbox folder is created and for as long as you're running the app, any files you move or copy there will be synced to the website and across your connected devices (if any) and will take up disk space on your computer normally.
The Dropbox folder is just another folder folder on your computer (only with syncing capbility) which takes up disk space, unless you choose to use our selective sync feature or the Smart Sync feature. Both of those features are a great way to free up disk space if needed.
Moving on to your concern, can you please let me know if you're getting any specific errors and in case you do, forward me a screenshot so I can have a visual as well?