Man it sucks when I'm having trouble like this.... stupid chest is burning so I can't sleep.
I would have to get the full game to be sure, but from what I can tell the problem is that the border is part of the game, it doesn't appear to be a smaller directx rect drawn in the center of the screen. I've done fixes where you find the rendering rect dimensions or in the case of fix it felix, the zoom level and altered things that way, but like I said, it appears at least to be all one render area.
Direct-x/Opengl games are really hard to magnify. The only solution I can think of would be some sort of a rendering hook. Maybe try a proxy dll system like SweetFX? I mean that's all I can think of.