Your computer is clean, infection has been removed. However, antivirus software you are trying to install fails to start, crashing or reporting an error... Check CommonAppData value in the registry, make sure it points to ProgramData folder on your system drive.
(32-bit operating system)
(64-bit operating system)
Right-click on the CommonAppData key and change its value to C:\ProgramData.
Sometimes infection is not as bad as mess it leaves behind - this simple fix took many long and frustrating hours to find.