Dell laptop Inspiron 15 with Vista Home Prem. System had a severe virus which has been cleaned but the virus may have affected some system files. I used an AVG Rescue Disk to clean the virus. I can now boot to normal mode but cannot boot to safe mode. Under normal mode, the system appears to behave correctly. Can anyone shed some light on why I cannot boot to safe mode? There is no error message, just a Welcome and rotating spiral. I have run chkdks /f and the process did remove some erroneous files. Your help is appreciated.