Do you mean that the index.dat files are not overwritten? CC cannot overwrite index.dat files as they are in use, and locked, by Windows. When Windows is running, that is. The files are scheduled to be deleted at pc boot time. When Windows initiates it reinstates new empty index.dat files. You can wipe the deleted files with Recuva. Some index.dat files seem to hang around and are not used: CC doesn't touch them.