The green tick indicates file/folder sharing. In my case, it was with Microsoft's OneDrive service (but it may be other software that provides a similar service).
If you are not worried about sharing to OneDrive, or similar software, removing the green tick is easy........
- Right-click on OneDrive icon in task bar and select 'Settings'
- Click on 'Account' tab
- Uncheck 'Start OneDrive with windows' box
- Click on 'Unlink this PC' - this will remove the account associated with the OneDrive service
Go back to your Desktop/folders and the green ticks will have gone :)
Process should be similar for other software that backs up to a virtual server - you will just need to look through the settings to find the right check boxes/links.