Sure,
Click in SIM to Options, Discovery and select Configure general setting. Here you can see serveral options like Automaticly discover VM guest(s) when the host is identified. ( this could be the first option). If you discover ranges this option would not work and you need to scrool down to the Enable discovery filters option. Here you could try the Limit discovery to systems wich meet the following criteria : Manageble systems with HP agents only.
This should stop virtuals without agent(s) to be added. It would have been nice if the was a subtype for virtual servers but i don't see such an option so this would be the next best thing.