According to this site ([http://blogs.msdn.com/b/dawate/archive/2008/02/05/building-a-3d-game-in-xna-from-scratch-free-video-tutorial-series-now-available.aspx][1]), the Guitar Hero buttons map directly to the standard control on an Xbox 360 controller. Here's what it says (has a video and everything):

>  10). Determining What's What On The Guitar Controller
> The controller for Guitar Hero games maps directly to controls on a
> standard Xbox 360 controller, but It's
> not immediately obvious what exactly
> the whammy bar, strum bar, and orange
> button do. Rather than go hunt for
> documentation, we can find out by
> experimentation in less than 5
> minutes.  
> Download WMV (4:45, 14.5 MB)

I haven't watched it, but I have seen other games that used a Guitar Hero controller in XNA. Good luck!


  [1]: http://blogs.msdn.com/b/dawate/archive/2008/02/05/building-a-3d-game-in-xna-from-scratch-free-video-tutorial-series-now-available.aspx