Ubuntu or Mint are great distros for first timers and OpenOffice Impress would probably be the best app to do a slide show.
http://www.openoffice.org/product/impress.html
Ubuntu and Mint are the easiest to install, especially if there is no operating system on the computer. Check out the link I gave you above, the application is free, and, if you want to experiment with it, there is even a Windows version if you don't have a Linux computer already set up.
BTW - If you are asking if the two different monitors can show 2 different displays, instead of a single presentation across 2 monitors, that's a bit more difficult, but probably could be done with a little bit of configuration.