title: Letterboxing in XNA on PC
body: <p>I know that when developing for Xbox in XNA, you basically just set the resolution to 1280x720 and the Xbox will just take care of things, but on PC I'm having some trouble getting the resolution handled correctly. </p>
  
  <p>I would like it to be able to run at other resolutions, but I'm actually happy to make the game always widescreen and just be letterboxed on 4:3 screens.  I can already handle scaling the game and it's components but I cannot figure out how to get it letterboxed.</p>
  
  <p>Obviously, this will not be necessary in windowed mode, but when running in fullscreen I just need to figure out how to get the game to only draw on part of the screen.</p>
  
  <p>What's the best way to do this?</p>