I have a small PC running as an XBMC attached to a Samsung le37m87bd. The PC isn't powerful enough to output a full HD 1080 image at 1920x1080 which is the TVs native resolution (about every 1/2 a second things go extra fast, I assume skipping frames), so I want to reduce this. Annoyingly, the TV does not support any other widescreen resolutions. (720 etc)

If I use a a 4:3 image, the TV stretches it to be the 16:9, however, all 16:9 content is stretched sideways as XBMC is sending out a 4:3 image with a 16:9 image inside. Is there anyway I can force XBMC to compensate for this, ie stretch vertically so that black bars are removed, but not stretched horizontally?