Multiple Singer Screen Monitors

[Gonzo]

At the moment, I am using a Dell Desktop as my show computer.
I use the VGA output for my screen and the built in HDMI output for the singers screen.

I would like to ALSO show the singers screen on the Big Screen behind us and perhaps the smaller tvs surrounding the bar.

I have a couple of different types of HDMI splitters that at the moment are not working (may just be a windows setting) but was curious if anyone else is running multiple monitors and how you are doing it?

Thanks!