How do I get black bars instead of screen stretching

Basically I want to play NFSU2 which for some stupid reason, doesn't support widescreen resolutions (my monitor is widescreen). The max resolution I can get is 1024x768 with it, and I don't mind that, but it stretches, and makes the cars look really wide and short which is really annoying. And the desktop stretches too when I select 1024x768. Basically I want black bars instead of stretching.

I'm using two GTX 460 768mb's, and a 1360x768 native resolution monitor (a new screen will be my christmas upgrade  )

Thanks!

(also, cant find a subsection for monitors  )