To use the shortcut, press and hold down your keyboards Shift key as you press Delete (or select the Delete command from a right-click drop-down menu). A confirmation request will pop up.

Hold "Shift" and press "Delete" to delete the file permanently without moving it to the Recycle Bin. Click "Yes" to confirm when Windows asks you if you want to permanently delete the file.

If you delete files from Dropbox and later change your mind, you have up to 30 days to restore and recover them.