

HKey_Local_Machine\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers in the navigator on the left-hand side.

These icons will only appear if the program is active.

However, you may run into an instance where these icons are not appearing as expected. In order to help you track the syncing status of your files, Box Drive and Box Sync put icons on folders and files in Windows Explorer showing "Synced", "In Process", and "Problem File".
