A video card that can handle as many monitors as you're driving. NOTE: running on two combined video cards yields arbitrarily poor results unless they are exactly the same model. Video drivers will often conflict otherwise.
Set your audience monitor(s) to 720p (1280x720). Do not set them to use Stretch Mode.
Microsoft .NET Framework v4.0 or newer is required. Depending on your system, you may need to download and install this framework.
Don't even try to use Windows with less than 2 GB of RAM. If you have any other apps you want to run at the same time (say, Powerpoint or Photoshop), best have at least 4 GB in your machine.