F@H is not a virus, by any stretch of the imagination what so ever. However, some "trojans" have stealthily installed a F@H client for the benefit of the trojan's originator.
Now, the proper way to uninstall the CLI-as-a-service is to shut down the service from the Services panel under Administrative tools, then go back to the folder where the CLI is and run it with -configonly, saying NO where it asks about running as a service. This will officially remove the entry from the registry.
However, you may well have screwed things up by deleting files so many times already, that you may just have to use regedit to get the F@H stuff out of your registry, if the proper method doesn't work. If the uninstall process is followed properly, things shouldn't be this hard.