MUSIC TROJANS

can anyone tell me why norton's didn't pick up 5 trojans that were on my son's computer.  Music kept playing on start up.  Rang norton's.  As per usual they were very helpful and I will still stay a customer, but problem stll persisted.  By adding the trojan names down hopefully norton's can add them to the search for malware.  c:\\windows\syswow64\adbcnsl.exe & HKLM\SYSTEM\CurrentControlSet\Services / &c:\\windows\system32\adbcnsl.exe & c:\\windows\temp\mrt30cf.tmp\stdrt.exe & HKLM\SOFTWARE\GOOGLE\chrome\Extrensv.  Hoping this will help all that read.