Peter,
You can use an Administrative command prompt to do so, for instance:
"sc delete MyService"
Will delete the service called MyService, refer to the Services Microsoft Management Console (services.msc) for a full listing and short name of the service in question.
This will unregister it as a service, but it will not delete it's binary, for that you must navigate manually to where the service resides.
I strongly recommend creating a System Restore point before doing any of this!