Several viruses create a new windows service, which activates the virus file , usually a DLL file. This is not visible in the Task manager. Hence it is hidden in the normal view. If you open the system configuration utility by using the msconfig command in the box that opens when you press Start > run . Or if the box is already open. When system configuration utility opens, Click on the Services tab. Click on the check box that says "Hide All Microsoft Services", that will reduce the number of services in the list. You can see if there is any service listed below, and if they are Checked, that is if they are active and running. You can stop these fake/ malicious services by uncheking the box in front of their name, and then press Apply, Ok/ close. And restarting the computer once. The actual file that this service utilizes need to be deleted and then use a registry cleaner like CCleaner to clean the registry entries. This way you can eliminate fake windows services and its associated files.