CCleaner wipes the data record of Microsoft Security Essentials that records when the last scan was run. As a consequence, MSE keeps saying I haven't done a scan lately and showing an orange icon, even though I do daily scans. According to Microsoft, this is because CCleaner wipes the record. It can be stopped by removing CCleaner from the Applications list, but it would obviously be better for new users if the scan data record was not removed in the first place.
Bob Frost