I use Plex for movies and shows but it doesn't work with live TV. Check out [url="http://www.nextpvr.com"]NextPVR[/url], it has a nice interface for live TV and is free. I use it as an addon to XMBC currently.
To answer your question:
Why are you going into 19:9? Do you mean 16:9? That might be your issue
Other than that, there should be an option to set zoom (maybe right-click?) or to constrain the aspect ratio.
Quote:
On the Windows Media Center start screen, scroll to Tasks, click Settings, click General, click Windows Media Center Setup, and then click Configure Your TV or Monitor.
Follow the instructions, and when prompted to choose a display width, click Standard (4:3) or Widescreen (16:9).
Select the appropriate display resolution, and then complete the instructions as needed. You might need to try more than one resolution setting to find the one that looks best on your display.
Source:
http://windows.microsoft.com/en-us/wind ... my-display