Just make sure that you have the latest virus defs and are actively scanning for Spy/Ad Ware. SVCHOST.exe can be running multiple instances on boot and this is totally normall. Although, vruses do disguise themselves as this service. The easiest way to tell is to try and end one of the SVCHOST.exe processes. Normally, since this is a system process you would get a "Access is Denied" message, but with a virus disguised as this process you will be able to stop it. At least them you'll know if you do, in fact have a virus.