Is there an inbuilt Windows 7 program available that will allow a screen share with a remote PC but can be configured so that the remote PC cannot have control of the host PC?
I don't believe that you can configure Remote Desktop to only share a your screen.
There is a quite simple way to accomplish this though. You should use one of the programs that people use to broadcast live streams of gaming and/or tutorials. XFire includes the ability to send out a live stream of your desktop.
Here's a tutorial on using XFire to broadcast a live stream: