If your viewing 4X3 video on your computer monitor "Fullscreen", and the par is 0.9, the physical "squareness" of the monitor will distort the image horizontally. Monitors don’t use the overscanning feature, (but some graphic cards will allow it). Therefore, it will "squish" the picture horizontally. Some software players may even compensate for it by letterboxing the 4×3 picture. The black bars would be very narrow and barely noticeable, thus preserving the true aspect ratio of the picture. Check your playback softwares setup menu and see if you can set it up that way. I don’t think Windows media player has this feature but I may be wrong. Also check your graphic cards set up. My ATI Radeon X1300 Pro allows for overscanning, but its currently off.
