yes, forceware can do it.. because there is an evidence here
http://www.hardforum.com/showpost.php?p=1029448840&postcount=811
how does it works ? well, my best guess is nvidia driver uses native res (like 1680x1050) and place the 4:3 ratio res (like 1024x768) inside it and upscale it...
@kevp,
I'd like to ask you regarding how you make black bars with nvidia control panel. Could you check the information (from the viewsonic OSD) about the resolution that is being used when you play using 4:3 resolution while maintaining aspect ratio? Yes i know you set something like 1024x768...