That could deduce to a resolution issue. FO1 & 2 run in 640x480. PC monitors usually downgrade their res to accomodate games like this, and then bring it back to spec after the program is closed. Not sure if your TV is rigged to behave the same way, or maybe it's just so frigging big your computer doesn't have the support
Try that res patch and see what happens, chances are the window wont change at all, just the resolution within it, but this would be a good first step.