Your PC SpeedCare software will run scans at certain scheduled times, however, you may choose to run a scan on YOUR time, whenever you want! You may want to run your own scans if you begin to experience lags in PC performance, or if you notice any error messages.
It is recommended running scans to ensure that any unwanted files left behind after your antivirus software removes a virus are completely gone. Sometimes, certain virus files somehow escape the eviction orders given during the antivirus removal process and they decide to take up residence elsewhere on your PC, for instance, in the Windows Registry. This unfortunate occurrence is not a rare situation and can sometimes happen.